462 Mr. G. H. Grosvenor. [Nov. 3, 



"On the Nematocysts of Solids." By G. H. GROSVENOK, B.A., 

 New College, Oxford. Communicated by Professor W. F. E. 

 WELDON, F.K.S. Eeceived November 3, Kead November 19, 

 1903. 



While I was at Plymouth in July, 1902, Mr. W. Garstang sug- 

 gested that I should investigate the origin of the nematocysts found in 

 Solids. He pointed out that no adequate account of their develop- 

 ment had been published, and that the view held by some that they 

 were derived from the Ccelenterate prey of the ^Eolids had never been 

 properly tested. In looking up the literature of the subject, I came 

 across Strethill Wright's abstract in the * Microscopical Journal/ 

 mentioned below, which convinced me of the advisability of a thorough 

 examination of the question from this point of view before attempting 

 to work out the development of the nematocysts in the ^Eolids them- 

 selves, especially as the few observations I had already made seemed 

 to point in the same direction. 



I. Historical. 



The cnidophorous sacs at the apices of the cerata of JSolids were 

 observed by Linnaeus and 0. F. Miiller. Cuvier and Oken took them 

 for suckers and Nordmann for mucous glands. 



Alder and Hancock (1) were the first to observe the expulsion from 

 these sacs of minute elliptical bodies provided with long hair-like tails. 

 They noted a considerable resemblance to spermatozoa, but observed 

 that there is no movement, and no apparent connection with the 

 reproductive system. 



These observations were continued by Hancock and Embleton (12)y 

 who give an accurate description of the " ovate vesicle," with its 

 external opening and ciliated canal, communicating with the " liver 

 C03cum." They also describe and figure the nematocysts of E. papillosa, 

 E. coronata, and E. olivacea, and their disposition within the " ovate 

 vesicle." They do not commit themselves to a definite opinion, bu 

 state that these bodies (the nematocysts) are " more like spermatozoa 

 than anything else " ; and they figure spermatozoa from the gonad 

 for comparison, stating that the chief difference between the two 

 are the more rounded body, and altogether inferior size of the 

 latter. 



By the time of writing the ' Monograph of British Nudibranchiata/ 

 Alder and Hancock had arrived at a true conception of the nature of 

 these bodies. 



Jn December, 1858, T. Strethill Wright read a paper before the 



