Written by A. W. S. on 26 September 1922
I can well remember collecting my first Pisidium. It was in a ditch in fields now long since built over by the extension of Belfast – but I still have the specimen – P. casertanum – and the Aplecta hypnorum that I collected with it. In those days Mr. Robert J. Welch was my only guide and friend and we kept a careful log of all our captures. It was then our custom to record our Pisidia as either "P. amnicum", "P. pusillum" or "P.sp ?". P. amnicum we did not often see, as our collecting was mostly done in areas beyond its range. "P. pusillum" we recorded without scruple as we thought it could do no harm, since the species was supposed to be ubiquitous. The other species we never dared to name.
It was with great joy, therefore, that when collecting near Sligo in September 1900, I heard Mr. Robert Standen name a Pisidium which we had found in an old limestone quarry. He said it was "P. roseum" (i.e. P. milium of course) and from that day I named P. milium with fair success. Also if a specimen was very inequilateral we could sometimes venture to call it "P. fontinale"; or if it was very clean and glossy it was "P. nitidum". About this time, 1898–1905, much of our material was sent to Mr. Charles Oldham whose naming was wonderfully consistent when we consider that he was trying to put ten or twelve species into five rather ill-defined forms. Not till the Clare Island Survey was started in 1909 and I had been asked to undertake the report on the L. and F.W. Mollusca did the problems of the Pisidia really assert themselves. During the survey I made many collections on oecological lines, which afterwards proved of the utmost value. I was saved, however, from floundering into the unknown, by learning that Mr. B. B. Woodward was writing a monograph on the British Pisidia and I was led to understand that he would be glad to see Irish material – though I have since discovered that I was mistaken on the latter point. Mr. Woodward being willing to name my Pisidia I naturally placed my Clare Island collections at his disposal, as it relieved me of the responsibility of trying to identify them – a task which I knew well I could not rightly undertake.
When we consider that Mr. Woodward’s chief experiences in the group were founded on the robust shells from the hard water of the Thames basin, the identification of those from the peat-covered areas of W. Mayo must have presented a most difficult and puzzling task, especially as he had seen little or no Irish material previously. Allowing for this, his recognition of P. hibernicum from Inishbofin was really an excellent piece of work. Naturally with the prospect of a monograph to help me I collected only Pisidia during the following years. With the long winter evenings of the country before me in 1914, I started with Mr. Woodward’s catalogue and specimens named by him to try and learn the hinge characters. This stage lasted through the winter of 1914–15 and was attended by several misfortunes, for it so happened that the specimens I chose for types of several species had been wrongly named by Mr. Woodward. Hence at the end of this first stage I was little further on in my studies. During the second winter I persuaded my friend Mr. R. A. Phillips to join me in the work and we compared notes and sent each other specimens to name. This, the second stage, lasted well into the year 1916 and ended in our throwing aside all Mr. Woodward’s identifications and starting afresh on our own lines. These lines were, to work oecologically, to see what species we could identify from certain restricted habitats and to see if our specific characters would hold good for examples from other habitats. Finally having isolated what we considered to be species, we tried to name these. My first habitat was a small stream, serving a water-mill, a little inland from Ballyhoime, near Bangor, Co. Down. In this I found three definite and distinct species, namely P. subtruncatum, P. nitidum and unfortunately P. hibernicum. I say "unfortunately" because at that time. owing to its supposed rarity, the finding of P. hibernicum seemed impossible and for more than a year I tried strenuously to regard it as merely a variety of P. nitidum. In 1916 Mr. Phillips sent a sample of sand dredged from the River Suir at Fiddown, near Waterford, and on examining this I found a single right valve of a minute Pisidium whose hinge characters were so distinct that I at once concluded that it was a new British species and guessed that it might belong to the P. parvulum of Mr. Woodward’s Catalogue. Other specimens were soon forthcoming and as Mr. Phillips agreed with me, in my opinion regarding its identity, we sent it to Mr. Woodward for his opinion. He replied that it was young P. supinum. The confidence we retained in our own opinion led to the breaking down of direct communication between myself and Mr. Woodward, who considered it was impertinent on my part not to accept his verdict, in spite of the fact that all my instinct led me to believe that these little shells were adults and not "mere fry". In attempting to rectify his position Mr. Woodward has complained that he has not been given an opportunity to alter his opinion in some cases of naming where I have had to point out that he was wrong. Possibly he has just grounds for complaint, but he must admit to himself, I think, that this state of affairs is due to his own actions in insulting us on the first occasion that we attempted to urge him to change his opinion about the identity of a Pisidium and this rendered future correspondence with him utterly out of the question. Two courses were left open to me to pursue. One, which I have followed, was to place in print the more important points that my researches led me to differ in from Mr. Woodward, the other was to drop my studies of the group completely – an achievement which, I cannot help thinking, Mr. Woodward hoped to attain by his letters to me. At least I can put no other possible interpretation upon it. My only aim has been to clear away the mist which enshrouded the specific characters of the Pisidia. Mr. Woodward seems always to assume that my interests lie with him, whereas on the contrary they are wholly with the Pisidia. In order to prove that the shells, which we considered to be P. parvulum of Woodward’s Catalogue, were not merely young P. supinum, I enlisted the sympathy of Mr. Charles Oldham, who sent me at the first opportunity living specimens of both species, which at once confirmed our previous conclusions, which in 1921 Mr. Woodward has had to accept (Proc. malac. Soc. Lond. 14: 209–220). Had he not lost control of his feelings we could have proved this to him in 1916. Mr. Oldham’s dormant interest was by this means aroused and since that date he has formed with Mr. Phillips and myself a small but exclusive Pisidium Club. The notes which follow are the result of our joint labours. Both my colleagues being men whom I must describe as too damnably modest for words, it has fallen to my lot to put our results down on paper; in the hope that they may at a future time be of some use to a student of the genus and that they may save his time or otherwise help him in his researches, not that we believe for a moment that they represent anything approaching the last word on the subject. From personal experience I have a little advice to give to all students. Satisfy yourself about all points of evidence before using it or building on it! Do not be bluffed by self-appointed authorities who thunder opinions at you before an audience that is unable to criticise their work, but who refuse to discuss these opinions with you. Authorities who, perhaps, never collected living Pisidium in their lives, and who, to cover up this lamentable fact, record shells not under the name of the collector, through whose generosity they obtained their material; but under the names of the persons in whose collections the shells temporarily rest – usually their own collection. Always help the beginner, if for no other reason, than in the hope that he will one day, like the mouse in the fable, be in a position to cut the net which entangles you!
In conclusion I say that I have no doubt that in time to come many "species" will be added to the British list but I cannot avoid hoping that breeding experiments may eventually prove that the species herein recognised are really species in the generally accepted meaning of the word and not composite agglomerations of diverse forms. If I may offer a suggestion to future workers, go in for breeding! Take a plastic species like P. casertanum from a standard locality where it is fairly constant and breed its progeny for a number of generations under different environments and see what happens!