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HANDBOOK OF INVERTEBRATE ZOOLOGY. 



Considerable change has now taken place in the shape 

 of that portion of the yolk which is contained in the head. 

 It is reduced to a long, narrow tube {y"), which connects 

 the portions contained in the body proper {y'" , y""), with 

 the external yolk sac (jj'). The pulsatile space (x), be- 

 tween the outer wall and the surface of the yolk sac, is 

 more plainly shown in this figure than in the preceding 

 ones, although a profile view shows it with equal distinct- 

 ness at earlier stages. 



Fig. 202 is a posterior view 

 of an embryo a little older than 

 the one shown in Fig. 201. A 

 large rounded prominence on 

 ench side of the head marks the 

 position of the eye-stalk, and the 

 eyes are farther forward than 

 they are in older specimens, but 

 in other respects the form is very 

 similar to that of the adult. The 

 ink sac {i) has appeared, and is 

 filled with ink, and the tip of the 

 free portion of the rectum is pro- 

 longed at its corners into the pair 

 of ear-like anal valves. 



Fig. 202. — A free swimming squid, 

 witli the external yolk entirely ab- 

 sorbed. (Drawn from nature by W. K. 

 Brooks. ) 



Fig. 202 



The letters as in the preceding fig- 

 ures. 



There are considerable individual variations in the ar- 

 rangement of the chromatophores, but there are certain 



