300 



ZOOLOGY. 



The arrangement of the Tentral system of arteries is yery 

 peculiar and quite characteristic of this animal. The oeso- 

 phageal nervous ring, and in fact the entire nervous cord, is 

 ensheathed in a vascular coat, so that the nervous system 

 and its branches are bathed by arterial blood. The veins 

 are better developed than usual : there being in the cephalo- 

 thorax two large collective veins along each side of the in- 

 testine. 



Closely connected with the two large collective veins are 

 two large brick-red glandular bodies each with four branches 

 extending up into the dorsal side of the cephalo-thorax. 

 They are probably renal in their nature. 



Both the ovaries and testes are voluminous glands, each 

 opening by two papillae on the under side of the first ab- 

 dominal feet. At the time of spawning the ovary is greatly 

 distended, the branches filled with green eggs. 



Unlike most Crustacea, the female king-crab buries her 

 eggs in the sand between tide-marks, and there leaves them 

 at the mercy of the waves, until the young hatch. The eggs 

 are laid in the Xorthem States between the end of Mav and 



Fic.266. 



Fl& 387. 



Fig. 266.— Embryo of King-crab, enlaiged ; am^ eeroos membrane ; ch, chorion. 

 . Fig. 267. — The same, more advanced. 



early in July, and the young are from a month to six weeks 

 in hatching. 



After fertilization the yolk undergoes total segmentation, 

 much as in spiders and the craw-fish. When the primitive 

 di.?k is formed the outer layer of blastodermic cells peels off 

 soon after the limbs begin to appear, and this constitutes 



