24 JEFFERY : ON THE HAIRS OF MOLLUSCA, &C. 



And secondly, Mr. Adams in his ' Collector's Manual ' 

 (see J.C., vol, iv., p. 318) credits Planorbis albus with the 

 possession of ' rows of minute hairs, running in a spiral direc- 

 tion,' and gives a special figure illustrating them as seen under 

 a powerful lens. I fail to detect them with the aid of my 

 microscope, and cannot help thinking that Mr. Adams must be 

 mistaken. 



To illustrate my paper, I send micro-slides, roughly 

 mounted, as follows : — shells of H. aculeata, H. pulchella var. 

 costata, and P. nautileus var. costata ; portions of shells of If. 

 rufescens, H. hispida, and H. sericea, ; hairs of H. sericea and H. 

 obvoluta; also twelve specimens of Z. stagnalis, from garden 

 ponds ; two L. stagnalis and two Z. peregra, with conferva 

 attached ; three Z. auricularia var ? also from garden ponds ; 

 and three Z. stagnalis from the other pond, in which latter the 

 shells are naturally clean, some with whitish markings. And 

 I trust that with these you may be able to follow my ideas, and 

 agree with my theory on the hair formation, so far as I have 

 been able to form one with the time at my disposal and the 

 opportunities at hand, and if I have stirred up a desire in any 

 member to go further into the matter (or to correct me where 

 I may be in error), I shall consider that some little good may 

 result from my investigations and the explanation of them. 



Mr. L. E. Adams has kindly sent me a hispid specimen of 

 Planorbis albus, and I note that Dr. Jeffreys in describing this 

 shell writes, ^^ epidermis thick, sometimes hispid or bristly," 

 while in Gray's Turton it is figured as bristly. There would 

 appear, therefore, to be two forms of this shell, and it would 

 be interesting to ascertain which is the more widely distributed. 



Mr. Adams has also called my attention to the fact that 

 the young of H. cantiana are hispid, this I have formerly 

 noticed, but it escaped my attention at the time I was writing 

 my address. 



J.C., v., January, 1886. 



