

CLASSIFICATION OF THE ANIMAL KINGDOM. 183 



above enumerated, the Cephalopods possess four salivary glands which com- 

 municate with the mouth, and, with the exception of Nautilus Pompilius, 

 they all possess a remarkable organ situated in the vicinity of the anus, 

 from which they can, when assailed, pour out a secretion of a dark inky 

 colour, and thus, by rendering the surrounding fluid opaque and turbid, 

 escape from their pursuers. The Cephalopods also possess the first rudi- 

 ments of an internal osseous skeleton, the principal part of which is situated 

 in the head, enclosing the oesophagus and brain, and corresponds with the 

 cranium of a vertebrate animal. Besides the senses of touch and sight 

 indicated above, this class possesses a slight sense of smell, and in the 

 Dibranchiate order we find also a rudimentary type of an ear. The branchial 

 organs consist of a central stem with broad vascular lamellae, and are situated 

 within the bag enclosing the viscera, and this respiratory apparatus is not 

 only used for aerating the blood, but, by its alternate drawing in and 

 expulsion of the surrounding medium, it forms one of the principal means 

 of locomotion, by jerking the body of the animal through the water back- 

 wards. The circulatory system is very complete, and in the Dibranchiate 

 order two distinct hearts are found, one on each side of the body. As 

 regards their generative apparatus, all the Cephalopods are dioecious, and. 

 in both sexes these organs present a structure peculiar to the class. The 

 eggs of the Common Cuttle-fish, (Sepia officinalis,) are of a black colour, 

 and somewhat resemble a bunch of grapes. From what has now been 

 stated, we shall naturally expect to find a nervous system of a far higher 

 development than anything we have yet met with, in accordance with the 

 superior general organization of the class we are considering, and such, of 

 course, is the case. The principal encephalic ganglion, which, as Professor 

 Jones observes, "is now from its size and structure fully entitled to be called 

 a brain," is enclosed in the cartilaginous skull already mentioned, and, as 

 in the Pteropoda, forms a ring enclosing the oesophagus; in this respect, 

 therefore, it is inferior to the brain of vertebrate animals, and accords 

 still with the Heterogangliate type of this organ; for, although now united 

 into one mass, yet this is effected only by the gradual concentration and 

 necessary enlargement of the ganglia met with in the lower orders of this 

 class, and presents somewhat the same analogy to them as the concentrated 

 nervous system of the butterfly does to the more numerous ganglia of the 

 caterpillar. Prom this nervous ring are given off cords, which communicate 

 with the optic ganglions, now considerably developed, especially in the 

 Dibranchiate genera, and also nervous twigs to the remaining organs of 

 sense and other parts. In addition to these, we find also nervous ganglionic 

 masses of considerable size distributed in different parts of the body, which 

 supply the muscles and viscera, and are variously developed, in proportion 

 to the importance of the organs over which they preside. 



(* To be continued.) 



