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 developmenl. if the skin is torn away and the vitelline 

 sack detached, one can introduce to ihe 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 thai of the adults. The xebra-like black 

 bauds are not seen, but the general liui changes insiautly 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 adulls. but ascend and descend more fre- 

 quently. 



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

 pupil representing exactly a ). It is furnished with an upper 

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

 lid; there is also a very distinct, palpebral sinus. 



In the I'oulpe (Octopus) ihe pupil is transverse and rounded 

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

 the ( .alamaries. 1 have not been able io si udy their eye living, 

 on account of the extreme mobiliiy 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 aduli Sepias was dilated 

 from seventy to severny-; wo :imes a minute, but in the young, 

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

 This result surprised me; it conlirms. for animals of variable 

 temperature, the law established for ihose of fixed temperature, 

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

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

 forty inspirations in a minute in the only individual which I 

 have examined, the si/e of which was inferior to that of most of 

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

 larger si/e. of the branchial sack of the Poulpe. which permits it 

 to introduce at one time a more considerable quantity of water 

 than the Sepia. 



