DEVELOPMENT OF THE EMBRYONIC RUDIMENT LOLIGO. 



255 l 



a circular swelling such as foreshadows the development of the arms 

 in L. vulgaris (Fig. llii B, dr). Further, in L. vulgaris, the indi- 

 vidual arms develop more distinctly in consecutive order, the first, 

 which appear as button like prominences, being those which lie next to 



R 



r.-Sd 



Fig. 116. — Various stages in the development of Loligo vulgaris (original). A, early 

 stage at which the eyes ami the shell-gland appear ; B, seen from the oral side ; G 

 and D, from the anal side. 1> is seen obliquely from above, and for the sake of 

 clearness, rather more of the yolk-sac is shown in this figure than is actually visible. 

 ar, rudiments of the arms ; ",-"-• lirst three pairs of arms ; au, rudiments of eyes, or 

 the swellings that carry the optic pits ; d, yolk; ds, yolk-sac; htf, posterior funnel- 

 folds ; k, gills ; between the two branchial prominences lies the rudiment of the anus ; 

 m, oral aperture; ma, mantle : ot, otocysts ; r, edge of the blastoderm ; sd, shell- 

 gland ; vtj\ anterior tunnel-fold. 



the funnel. At this period, the rudiments of various other organs are 

 already visible, the most striking of these being the paired branchial 

 fold (Fig. 116 C, /.) which lies immediately in front of the mantle 



