560 



CEPHALOPODA. 



ment of the embryo has commenced, and are 

 connected together in clusters by long filamen- 

 tary processes. 



in the figure subjoined, (fig- 240), A repre- 

 sents the ova of the natural size, B a group of 

 ova at an early stage of embryonic develop- 

 ment, magnified, C a single ovum, still more 

 highly magnified, showing the embryo a, the 

 rudimental feet &, and what would be regarded 

 as the vitellus c, in the ovum of any of the 

 naked Cephalopods, but which the continuator 

 of Poli states to be the germ of the shell. 

 With respect to the Poulp (Octopus) Aristotle 

 states that the animals of this genus copulate 

 in winter and bring forth in spring : that the 

 female oviposits in a shell or some secure 

 cavity; that the ova adhere in clusters, like the 

 tendrils of the wild vine or the ftuit of the 

 white poplar, to the internal parietes of the 

 cavity; that the young Poulps are hatched on 

 the fifteenth day, and are then seen creeping 

 about in prodigious numbers.* 



The ova of the Calamary (jig. 241) are in- 

 closed in cylindrical gelatinous sheaths, mea- 

 suring from three to four inches in length, and 

 about a quarter of an inch in diameter at the 

 thickest part, narrowing to an obtuse point at 

 one end, and attached at the opposite extremity 

 by a filamentary process, varying from half an 

 inch to an inch in length, to some foreign body, 

 as floating wood, &c.; each sheath or nidamen- 

 tum contains from thirty to forty ova, of a 

 spherical figure, about a line and a half in 

 diameter when newly excluded. As the num- 

 ber of cylinders attached to one body some- 

 times exceed two hundred, the prolific nature 

 of the species may be easily conceived. 



Fig. 242 shows the first appearance of the 

 head and eyes a, at the stage prior to the 

 development of the arms and funnel ; 6 is the 



Fig. 244. 



elongated body, c the yolk-bag. Fig. 243 

 is another ovum at a more advanced stage of 

 development : the pigmentum is now deposited 

 both in the rete mucosum and in the eye ; the 

 arms are just beginning to shoot from the ante- 

 rior circumference of the head ; and the little 

 funnel may be observed rising above the ventral 

 margin of the mantle. 



The ova of the Sepioteuthis are also spherical 

 and enveloped in cylindrical sheaths, but these 

 are much shorter than in the Loligo, and contain 

 much fewer ova, making an approach in this 

 respect, as in the general organization, to the 

 Sepiae, in which each ovum has its own nida- 

 mentum. 



The eggs of the Cuttle-fish (fig. 244) are of 

 an oval form, attenuated at the extremities, 

 enveloped in a flexible horny covering, of a 

 blackish colour, which is prolonged into a pe- 

 dicle at one extremity, and twisted round some 

 foreign body. The length of ovum from the 

 point of its attachment is generally an inch, 

 and as a number of these ova are always found 

 attached close together, and sometimes to one 

 another, they resemble in this state a bunch 

 of grapes, as the name t sea-grapes/ com- 

 monly given to them by the fishermen, implies. 

 In the development of the Cephalopod the 

 most interesting circumstance, and one which 

 had not escaped the notice of Aristotle,* is the 

 point of attachment of the yolk-bag (c,Jig- 245), 

 which is suspended from the 

 head of the embryo, its pe- 

 dicle being surrounded by 

 the cephalic arms,and passing 

 down anterior to the mouth 

 to communicate with the 

 pharynx. The yolk is a trans- 

 parent gelatinous fluid of a 

 spherical form. 

 In the embryo of the Cuttle-fish all the 

 organs, the exercise of which is essential to its 

 future welfare, are adequately developed before 

 its exclusion. The gills are very distinct, and 

 the respiratory actions are vigorously performed 

 by the alternate dilatation and contraction of 

 the mantle and a corresponding elevation and 

 falling of the funnel (d), by which the little 

 streams are expired. The ink-bag has already 

 provided a store of secretion sufficient to 

 blacken a considerable extent of water, and 

 baffle any enemy which may be ready to remove 

 the little Cephalopod from the world into which 

 it is about to enter. The pigment of the rete 

 mucosum is developed in several large spots, 

 as in the Calamary (Jig. 243). 



Five concentric layers of the dorsal shell at 

 least are deposited ; these are, however, horny, 

 white, and transparent, except at the narrow 

 and thick end; and the innermost layers are 

 marked with irregular opake spots. The lateral 

 fins are broad, and the ventral arms are furnished 

 with a fin-like expansion, so that the young 

 animal is enabled to execute movements either 

 retrograde or progressive ; and the eyes are well 



Foetal Sepia. 



Ova of the Cuttle-fish, Sepia OJficinalis. 

 * Hist. Animal, lib. v. cap. 16. 



priore. 



Adhaeret ovo Sepia nasceus parte sui 

 De Generatione Animalium, lib. iii. c. 8. 



