HABITS OF THE CEPHALOPODA. 01 



Aristotle, l)ut tlie exi)laiiatioii which \w oivcs is mort' than 

 doubtful. The very o])aquo and \v\-\ dark skin of the excluded 

 egg, later becomes thinner and neai'ly translucid. At the last 

 period of developnicnl. if llie skin is torn away and the vitelline 

 sack detached, one can introduce to the world, as I hav(> often 

 done, the young 8epia. It swims immediately, and changes 

 color with the greatest facility. 



The coloration of the Sepias several centimetres in length is 

 more variable than that of the adults. The zebra-like- black 

 bands are not seen, Init the general tint changes instantly from 

 gray to wine-brown, to violet, to green. The young Sepias sink 

 into the sand, only showing a part of the back and the head ; 

 they swim like the adults, but ascend and descend more fre- 

 quently. 



The eye of the Sepia has a very strange appearance ; the dark 

 pupil representing exactly a to. It" is furnished with an upper 

 lid, colored by chromatophores, and a narrower, whitish under 

 lid ; there is also a very distinct palpel)ral sinus. 



In the Poulpe (Octopus) the pupil is transverse and rounded 

 at its extremities. I have never seen it change its form. As to 

 the Calaniaries, I have not l»een able to study their eye living, 

 on account of the extreme mol)ili[y of these animals. 



The sea-water destined for respiration enters the cephalic 

 extremity of the branchial sack, and leaves l)y the siphon. The 

 alternate movements of the openings of the sack and si})hon can 

 be readily seen. 



The branchial sack in a nund)ei- of adult Sepias was dilated 

 from seventy to seventy-two tiines a ininute, l)ut in the young, 

 about an inch long, the inspirations reached 140 in a minute. 

 This result surprised me ; it confirms, for animals of variable 

 temperature, the law established for those of fixed temperature, 

 that the numljer of inspirations is in inverse ratio to the age. 

 The Poulpe respires more slow ly ; I only counted thirty-eight to 

 forty inspirations in a minute in the onh' individual which I 

 have examined, the size of which was inferior to that of most of 

 the adult Sepias. This ditference is due, perhaps, to the much 

 larger size of the branchial sack of the Poulpe, which permits it 

 to introduce at one time a more considerable quantity of water 

 than the Sepia. 



