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HANDBOOK OF INVERTEBRATE ZOOLOGY. 



of the siphon have completely united with each other, 

 and at the point of union the siphon is also united to the 

 body wall, and the retractor muscle of the siphon (Fig. 

 198, sm), now runs back to unite with the inner anterior 

 surface of the mantle. The otocysts have almost met each 

 other upon the median line, under the siphon, and their 

 walls are now very thin. The eye-stalks are prominent 

 at this stage, but they soon begin to 

 disappear. 



The embryo shown, from the right 

 side, in the next figure (Fig. 200), 

 has assumed the general form of the 

 adult, and the eye-stalks have almost 

 disappeared, although, as shown in a 

 posterior view (Fig. 201), the eyes 

 are very prominent still, and are di- 

 rected more towards the ventral sur- 

 face than they are in the adult. 



Fig. 199. — Posterior surface of a somewhat 

 older embryo. (Drawn from nature by W. K. 

 Brooks. ) 



e. Eye. i. Ink bag. r. Rectum. The other 

 letters as in Fig. 195. 



The mantle now covers about one-half the entire length 

 of the embryo, exclusive of the yolk-sac, and the neck- 

 cartilage {7ic), has made its appearance, forming a support 

 for the edge of the mantle, on the middle line of the ante- 

 rior surface of the head. The posterior surface of the 

 mantle is now pretty well covered with chromatophores, 

 which at this stage possess remarkable power of expan- 

 sion and contraction, and render the living eml)ryo a very 

 beautiful and wonderful sight under a low magnifying 



