same manner as does the backbone in vertebrate animals. The pen was 

 nearly a foot in length, and much resembled a quill or bird's feather, from 

 which it receives its name. It is formed of a stout central shaft, which 

 reaches nearly to the lower end, and has a thin blade on each side. It lies 

 in a pocket, or capsule, in the dorsal side of the squid, but is not 

 attached to it by any muscles. The octopus does not have this inter- 

 nal skeleton, because it lives about rocks and on the bottom of the 

 sea, while the squid and cuttlefish are pelagic, or free swimmers, 

 and therefore need some sort of support for their soft 

 bodies. 



Procuring a pan of water, Professor Parker immersed 

 a large squid, cut the skin or mantle from the upper 

 edge or collar to the pointed posterior end, turned back 

 the several pieces, and exhibited to us the internal organs. 

 We saw that the mantle was attached to the head in 

 three places by a set of cartilages, those on the mantle 

 fitting into those on the head like a long and narrow 

 button and button-hole. One cartilage was on the upper 

 or dorsal side, in the center, and two were on the ventral 

 side on the siphon. 



We were told that the inside of the animal is called 

 the mantle cavity, and we were shown that it contains 

 the heart, gills, nervous system, digestive system, and 

 all of the vital organs. We found the siphon to be made 

 up of three chambers ; a funnel-shaped ventral chamber 

 opening into the mantle; and on either side a chamber 

 which opens into the mantle chamber, but not on the 

 outside. By this arrangement. Professor Parker said, 

 the water contained in the mantle cavity is compelled 

 to pass through the ventral chamber, as the lateral cham- 

 bers, having no outlet, are forced against the sides of the 

 mantle chamber, causing it to close; and thus the siphon is made an 

 important organ of locomotion, for when the water is thus forced out, 

 the animal shoots backward. Near the base of the siphon we saw 

 the little oval ink bag. The large gills and venos cavse were the 

 only organs which seemed to be attached to the mantle, and the 

 posterior part of the body was made up of the large visceral sac, which 

 contains the stomach, liver, and other organs. 



Having learned what we could about the squid, we helped Profes- 

 sor Parker prepare the rest of the specimens. To do this, a slit was 

 cut in the mantle, so that the liquid might reach the internal organs, 



129 



Pen, or inter- 

 nal support of 

 squid. Notice 

 the long, nar- 

 row, central 

 shaft, and the 

 wide margin on 

 each side. (Ver- 

 rill.) 



