Martin, A Noto on the Occurrence of Nematocysts and Similar Structures etc. 267 



(4) Those Aeolids (Janidae,' Fionidae and Calma glaucoides) which 

 habitually feed on animals other than Coelenterates have no 

 nematocysts. 



(5) Though several have tried, no one has succeeded in giving 

 even a plausible account of the development of nematocysts 

 in Aeolids. 



(6) This view affords a satisfactory explanation of the function 

 of the ciliated canal through which nematocysts and other 

 indigestible bodies have been observed to pass from the gastric 

 diverticulum of the cnidosac. 



(7) A repetition of Strethill Wright's experiments gave entirely 

 confirmatory results. In one case three R. peregrinas, having 

 only small pip-shaped nematocysts in their cnidosacs, were 

 fed on Penrtan'a C'arolimi, the nematocysts of which, after a 

 month, had almost entirely replaced the original pip-shaped 



ones." 



Grosvenor's results have been amply confirmed by Cue not. 



In the case of the Cleptocnids of Aeolids it is interesting to 

 note that these structures are undoubtedly used defensively by their 

 possessor. Grosvenor stated on page 476. 



"In this way a fish which had snapped at the cerata, the loss 

 of which, as is well known, does not seem to inconvenience the 

 Nudibranchs at all, would receive a discharge of nematocysts into 

 its moulh, where they would probably act with the greatest possible 

 effect. This is in complete agreement with Garstang's view as 

 to the meaning of certain features in the coloration of Aeolids. 

 He suggests that the localisation of the bright colours in th^ cerata 

 'serves to direct the experimental attacks of young and inex- 

 perienced enemies to the non-vital papillae and away from the 

 vital and inconspicuously coloured parts of the body', and 'at the 

 same time gives them (the enemies) the needful experience of the 

 unpalatable nature of their intended prey' ([9] p. 175). The erection 

 and el6ngation of the cerata conduce to the same result (i. e. make 

 them the most probable mouthful for an enemy), even when the 

 bright colours are absent or otherwise disposed." 



Cleptocnids of Cephalopods. 



The only other instance as far as I am aware of the occur- 

 rence of Nematocysts in the Mollusca is that in a Cephalopod, 

 Trewoctopns nticrostoina which is described by Bedot in his "Note 

 sur les Cellules Urticantes" in the Rev. Suisse de Zool. et Ann. 

 Mu. D'Hist. Nat. Geneve, Tome III, page 088. 



"Troschel a decrit chez le Tremoctopus inicrostotna Reynaud 

 (Philoxeiiix tnicrostotnus Troschel) un fait tres curieux. Des eylin- 

 dres transparents, garnis des cellules urticantes, sont fixes par les 



