HABITS OF THE CEPHALOPODA. 61 



Aristotle, but the explanation which he gives is more than 

 doubtful. The very opaque and very dark skin of the excluded 

 egg. later becomes thinner and nearly translucid. At the last 

 period of development, if the skin is torn away and the vitelline 

 sack detached, one can introduce to the world, as I have often 

 done, the young- Sepia. 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 arc not seen, but 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 co. It is furnished with an upper 

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

 lid ; there is also a very distinct palpebral 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 (-alamaries, I have not been able to study their eye living, 

 on account of the extreme mobility of these animals. 



The sea-water destined for respiration enters the cephalic 

 extremity of the branchial sack, and leaves by the siphon. The 

 alternate movements of the openings of the sack and siphon can 

 be readily seen. 



The branchial sack in a number of adult Sepias was dilated 

 from seventy to seventy-two times a minute, but 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 number of inspirations is in inverse ratio to the ai>v. 

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

 forty inspirations in a minute in the only individual which 1 

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

 the adult Sepias. This difference 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. 



