^^229. 



THE CEPIIALOPIIORA. 



2G7 



of the entire surface of the vitellus, but surrounds the last in a ring-like 

 manner, and is gradually detached by its cephalic and caudal extremities. 



pacious portion are found both male, (testes), and fe- 

 male (ovarium) organs in the shape of sacs, which 

 are not attached iu any way to the main moUuskig- 

 erous sac. These genital organs bear no resem- 

 blance whatever to ordinary testes or ovaria, except 

 in their products, which are identical. When the 

 ovarium is perfectly developed, it and its capsule 

 burst and discharge the ova which are then con- 

 tained in the main molluskigerous sac ; after this, 

 fifteen to twenty ova become invested with a com- 

 mon capsule, though their fecundation takes place 

 previous to this mvestment. Upon this succeeds 

 their development. 



The sperm- capsules vary from four to eighteen in 

 number, and lie perfectly free in the main sac, not 

 far from the ovary. The spermatic particles are 

 set free by the bursting of these capsules, and they 

 resemble those of the Gasteropod MoUusks in shape 

 and form. 



The development in the egg here proceeds exact- 

 ly as with the Mollusca(e. g. Actaeon, according to 

 Vo^t), and finally it assumes pretty definite char- 

 acters indicatmg rather its relation to the Pectini- 

 brauehia. Of its zoological character as a Mol- 

 lusk there can, therefore, be no doubt, and the whole 

 story in a word is, that a true MoUusk is developed 

 within a Sytiapta, not by gemmation, but by 

 means of the normal sexual products which occur 

 under otherwise amorphous and anomalous parts 

 and conditions. It should, moreover, be remarked 

 that the connection of this molluskigerous sac is 

 not special or dh-ect with the Synapta, but this last 

 appears to serve as a kind of nest in which the 

 Mollusk carries out its ulterior and remarkable 

 changes. 



Such being the facts, the question now arises. 

 What interpretation shall be given these phenome- 

 na .' The distinct sexual mode of reproduction 

 would seem to remove these phenomena from the 

 category of the so-called alternation of Generation, 

 or gemmiparity as we now understand it. Then 

 again, the doctrine of " heterogeneous generation " 

 as suggested by Miiller, does not seem to me ad- 

 missilile, beside being particularly unsound, — for 

 if an animal can produce, by true sexual generation, 

 an offspring zoologically dissimilar to itself, zoolo- 

 gists may well look about for the stability of theu- 

 science. If I may be allowed an opinion or rather 

 a view on a subject on which I have made no ob- 

 servations, Iwould say that an approximate solu- 

 tion of this enigma seems obtained by admitting the 

 possibility of new and hitherto unknown parasitic 

 conditions in the life of the Mollusk in question. 



Why may not this Mollusk undergo a form of 

 retrograde metamorphosis during which its life is 

 parasitic and very peculiarly connected with the life 

 of another and wholly different animal .' Or again, 

 why may not the phenomena observed be the final 

 conditions of certain low modes of life which are 

 connected with points in the economy of these 

 animals that we do not yet understand ? I throw 

 out these remarks in a suggestive way. If we re- 

 fer for a moment to the historical relations of the 

 Cestodes, it will be perceived that there was a time 

 when the conditions of then- life were equally if not 

 more obscure. Siebold^ however, has shown that 

 here, although the path taken by Nature is circuit- 

 ous and intricate, yet, after all, no new features of 

 a heterogeneous nature are introduced, and that 

 all required for the observer was care and pa- 

 tience. It does not seem to me any more im- 

 probable that this Mollusk should have entered iu 

 some of its stages the body of the Synapta, since 

 the anomalous undeveloped forms of many Hel- 

 minthes pursue a similar course. Let the natural- 

 ist also bear in mind the remarkable phenomena of 

 the Hectocotyli. In the Nachtrag to this first ac- 

 count before the Berlin Academy, but more espec- 

 ially in a subsequent and more complete account 

 (Ueber die Erzeugung von Schnecken in Holotbu- 

 rien, in Miiller^s Arch. 1852, p. 1) lately given, 

 Miiller discusses stiU further these facts. After 

 some remarks upon the importance of a careful 

 study of the embryology of this curious form, he 

 says : " I do not give up the hope that we may yet 

 determine at least the genus of this Mollusk ; and I 

 found this hope mainly upon the very characteris- 

 tic form of the spermatic particles, beside the other 

 features above mentioned The sperm- 

 atic particles of Natica and its allies are yet un- 

 known In studies bearing upon this mat- 

 ter, one should particularly bear in mind the ter- 

 minal enlargement of the spermatic particles, w'lich 

 up to this time has been observed in no Gasteropod, 

 but which with the spermatic particles of the Mol- 

 lusk in question is never wanting." Although for 

 some time familiar with the details of the spermatic 

 particles of the Gasteropod MoUusks, yet I have 

 very recently reexamined the spermatic particles 

 of Natica (If. heros) with reference to this point. 

 They resemble closely those of the pulmonary Gas- 

 teropoda (Helix, for instance), and consist of a well- 

 defined cork-screw head to which is attivched a 

 very delicate tail ; they agree, therefore, in general 

 with the form given by Miiller of the MoUusk in 

 question. — Ed. 



