374 LOWER INVERTEBRATES. 



the eye has an imperforate cornea, ten arms (one pair tentacular) which in the female 

 bear six rows of minute suckers, but none in the male. The body is oblong, with 

 minute terminal fins ; the female has an oviduct on the right side*, and two nidamental 

 glands ; in the male no hectocotylus is formed. Spirula is the only genus. 



Although on some shores the dead shells are washed up by thousands, the animals 

 are among the greatest rarities in the animal kingdom. Only three perfect, and a few 

 mutilated specimens have as yet been found. Our knowledge of the anatomy is al- 

 most wholly due to Owen, whose papers on the subject are models in the line of re- 

 search with very limited material. The shells of Spirula fragilis are occasionally cast 

 up on the outer shores of Nantucket, while a living specimen was dredged by the U. 

 S. coast survey in the West Indies in 1878. It came from, a depth of nine hundred 

 and fifty fathoms. Spirula peronii and S. australis come from the Indo-Pacific and 

 Australian seas. 



The family Sepiad^ embraces the true cuttle-fishes, in which the internal shell is 

 calcareous, the cornea imperforate, the body oval, with long fins, the tentacular aims 

 very long, and capable of being completely retracted into pouches at the base ; in the 

 male, the left arm of the fourth pair is hectocotylized. The only genus, Sepia, is the 

 one which furnishes the cuttle-bone which is found thrust between the bars of every 

 canary cage, and whose ink is the basis of the pigment sepia. This is still manu- 

 factured in Rome. The cuttle-fishes are essentially littoral animals and are extensively 

 caught, not only for the ink and the bone, but for the sake of the flesh, which is used 

 as food. 



The animals, when undisturbed, swim rather slowly and gracefully by means of 

 undulations of their fins, but when startled or alarmed, the siphon and the arms are 

 worked as in the case of Octopus, and then the fins are wrapped tightly around the 

 body. They lay their eggs in black egg-shaped or pyriform capsules attached to sub- 

 merged objects. They feed upon fishes, crabs, and molluscs. As in all cephalopods, 

 the colors are changeable, but in Sepia officinalis zebra-like bands of blackish brown 

 cross the body. 



With the family Loliginid^ we take up some of the squids in which the body is 

 more or less conical, tapering to a point behind. The fins are large, sometimes extend- 

 ing the whole length of the body. The cornea is entire, the eyes without lids, the 

 tentacular arms but partially retractile and distally furaished with four rows of 

 suckers, while on the other arms there are but two rows. The fourth arm on the left 

 side is hectocotylized at the tip. The pen is long, slender, and flattened. Three living 

 genera are known, only one of which, Loligo, is represented on our coasts ; Sepioteu- 

 thus occurs in the West Indies, and JLolioliis in the Pacific. Loligo pealei is the com- 

 mon squid south of Cape Cod ; it extends south to the Carolinas, but north of the 

 Cape it is not so common as Ommastrephes illicebrosa. A second species, X. brevis, 

 extends from Virginia to Brazil, while X. galei occurs in the Gulf of Mexico. The 

 anatomy, habits, and external development of the former species are pretty well 

 known. They lay their eggs dui'ing the warmer months of the year, in large bunches 

 of gelatinous capsules which are usually attached to some algse. The young develop 

 rather rapidly, and at certain times are taken in large numbers in the surface net. 

 They are eagerly eaten, not only by fishes, but by the larger individuals of their own 

 species. None of the squid ai-e used in America as food, but immense numbers are 

 caught and used as bait by the fishermen. 



The SepiolidjE are closely related to the last family, but differ in having a short, 



