300 



THE CEPHALOPODA. 



§261. 



mouth, and producing a communication between the internal and external 



sacs. 



The vitellus of the internal sac gradually disappears, and is replaced 

 through this canal of communication by that of the external sac. During 

 the successive development of the organs contained in the cavity of the 

 mantle, the internal vitelline sac is divided into lobes which are finally broken 

 up and absorbed ; while the intestinal canal, the remaining organ of the 

 embryo, is developed, quite independently, from the vitelline mass. 



As to the development of the males [Hectocotyli) of Argonauta and 

 Tremoctopiis, nothing is yet known except of its last period. It has been 

 observed, however, that, during the time they are in the egg, they have their 

 proper form which is so remarkably different from that of the females."'^ 



6 Had tlie fact that the Hectocotyli exist hi the 

 egg with their proper form, among the eggs of fe- 

 males of certain species, been properly observed, 

 the true relations of these supposed parasites to the 

 animals iu which they live, would have been known 

 long ago. A passage of Maravigno, first properly 

 interpreted by KoUiker (Ann. of Nat. Hist. loc. cit. 

 p. 414) shows clearly that this Italian naturalist, in 

 his researches connected with Argonauta, was in 

 error only as to the eggs which contauied the male 

 individuals. 



He says thus : " Mais encore que le petit poulpe, 

 au sortir de I'oeuf, ne ressemble pas enti^rement A 

 ce qu'il sera par la suite ; c'est alors vine sorte de 

 petit ver (vermicello) pourvu de deux rangees de 

 ventouses dans la longueur, avec un appendice fili- 

 forme A. une extremite, et un petit renflement vers 

 I'autre, oii il parait que sont les organes de la di- 

 gestion. "— (Ann. d. Sc. Nat. VII. 1837, p. ITS.) 

 The mode of development of these males differs 

 undoubtedly very much from that of the females.* 



* [ § 261, note 6.] The subject of the Hectocoty- 

 lus to which such frequent mention has been made 

 in these pages, is one that has elicited a good deal 

 of attention of late years, but, now, happily, seems 

 pretty definitely settled. Chief among these inves- 

 tigators are H. Miilter, and Verany and Vogt. 

 They have pretty clearly shown the non-independ- 

 ent character of these forms. The details of these 

 researches cannot here be given ; it may be re- 

 marked, however, that these observers have all 

 studied these forms upon living specimens on the 

 coast. It has been shown that the Argonautae on 

 which these Hectocotyli are found, have a highly- 

 developed testicle, the situation and structure of 

 which correspond to those of the common Cephalo- 

 poda, and which communicates with the Ilectoco- 

 tylus. 



In conclusion, I may quote H. MuUer's own 

 words : " It is then proved that the Hectocotylus 

 is formed on a male Argonauta, and is nothing but 

 an arm metamorphosed in a very irregular man- 

 ner. This arm, or the Hectocotylus, is detached 



when it has been filled with the sperm which is 

 formed in a true testicle of the Argonauta itself, and 

 it then plays an apjjarently independent life. In this 

 condition, it meets the female Argonautae which, 

 by a true copulation, it impregnates, as I have 

 observed with the Hectocotylus of a Tremoctopus, 

 and it resembles in this, as also by its movements, 

 by a kind of circulation, and by the long duration 

 of its life after detachment, a true male animal." 



I'or the literature of this subject, see, beside the 

 writings referred to in the above pages, KoUiker, 

 Transact. Linn. Soc. London, XX. 1846, p. 9, PI. 

 I. ; Bericht von der zootomischen Anstaltzu Wiirtz- 

 burg, Leipzig, 1849, p. 67, Taf. I. II; Power 

 {Madame) MoUusques Mediterraneens, Ire partie 

 Genes, 1847-51, p. 34, 126, PI. XLI. ; Virany and 

 Vogt, Ann. d. Sc. Nat. XVII. 1852, p. 146, PI. VI. 

 -IX. ; H. Mailer, Ann. d. Sc. Nat. 1852, XVI. p. 

 132 ; also, in extenso, in Siebold and KiiUiker^s 

 Zeitsch. IV. p. 1, Taf. I. and p. 346 ; and Siebold, 

 in Ibid. IV. p. 122. — Ed. 



