1903.] On the Nematocysts of Solids. 469 



Also two Amphorina ccerulea found on Sertularella ; a Facelina sp. 

 found on Antennularia ; a Cuthona aurantiaca and three Facelina wronata 

 on Tubularia ; Facelina punctata on Pennaria Cavolinii three Rizzolia 

 peregrina dredged with Eudendrium rameum; four Pdzzolia peregrina 

 dredged with Eudendrium sp. ; all had nematocysts indistinguishable 

 from those of the hydroid with or on which they were found. 



But it is possible in many cases where the " food hydroid " of an 

 ^Eolid is unknown, to prove that the nematocysts in the cnidosacs of 

 the ^Eolid are the same as those of its prey, whatever that prey may 

 be ; for it has been noted by several observers (Alder and Hancock, 

 Hecht, &c.) that the faeces of ^Eolids consist largely of nematocysts, 

 obviously derived from their food, but no one seems to have compared 

 them with those found in the cnidosacs. I have made this comparison 

 in a number of cases, and have always found the nematocysts in the 

 faeces identical with one or more forms which occur in the cnidosac. 

 In those individuals which have many different types of nematocysts 

 in their cnidosac, these are not always all represented in the fasces, for 

 the latter are extruded a day or two at most after the meal of which 

 they are the remains, while nematocysts may remain in the cnidosacs 

 for at least a month, as is proved by an experiment to be described 

 presently. 



4. Those ^Eolids which are known to feed on animals unprovided 

 with nematocysts have no nematocysts themselves : 



Thus the sub-family Janidse, many of which are known to feed on 

 Polyzoa (see Garstang (9) and Giard (10)), have no nematocysts. 

 Since these forms have also no cnidophores and in many other ways 

 are very aberrant, it might be objected that they branched off from 

 the ^Eolid stem before the acquisition of nematocysts by the latter, and 

 the fact of their feeding on Polyzoa was a mere " coincidence." This 

 objection, however, cannot apply to the case of Calina glaucoides. 

 This is in all other respects a typical ^Eolid, but, according to M. Hecht 

 (1), it has no nematocyst and no cnidosacs. According to the same 

 author there can be no doubt that the food of this species consists of 

 the eggs and embryos of various shore fish (Cotta, &c.). The only 

 other member of the genus Calma is C. Cavolinii, which has typical 

 cnidophores, usually crowded with nematocysts, and which feeds on 

 hydroids, for I have found unmistakable fragments of the same in 

 the stomachs of several specimens, as well as nematocysts in the 

 faeces. 



M. Hecht, seeking an interpretation of the coincidence of non- 

 ccelenterate food and absence of nematocysts in C. glaucoides, in the 

 light of the current opinion as to the origin of nematocysts in Nudi- 

 branchs, writes as follows: "On peut considerer 1'absence de sacs & 

 nematocystes chez C. glaucoides comme un pur phenomene de degener- 

 escence, e^ant donne qu'ils existent chez une espece voisine ; quant a 



