DEVELOPMENT OF THE EMBRYONIC KUDIMENT LOLIGO. 259 



ventral middle line (Fig's. 116-117). At first they form together 

 merely a slightly undulating line (Fig. 117 A), but their lateral ends 

 soon bend back further (Fig. 117 7?) and as the folds at the same 

 time swell up more, the later form of the funnel becomes indicated 

 (Fig. IIS A and /?). At the same time, the posterior funnel-folds 

 become modified in shape, now appearing forked at the point where 

 they come into contact with the anterior folds (Fig. 118 A). This 

 is caused by the rise of a new fold at this point, which runs towards 

 the mantle. This is, like the other folds, an expression of the 

 greater growth of the mesodermal tissue and represents a part of the 

 retractors of the funnel (muse, depressores infundibuli). 



ma 



au 



Fra. 117. Two stages in the development of Loligo wdyaris (original). .1 , seen from 

 the anal or funnel-side ; />', obliquely from above. (The remarks made on Fig. lib' 

 l> apply to />') "i ".-;, first three pairs of arms; av., optic swelling; ds, yolk-sac; 

 ///;, posterior funnel-fold ; k, branchial folds or gills ; ma, mantle ; nk, nuchal carti- 

 lage ; (, otocysts ; rtf, anterior funnel-fold. The circular fold out of which the 

 ana-rudiments arise can still be recognised, especially in A. In tt, the long promi- 

 nences indicating a pair of arms (lying behind a s ) still form part of it. The funnel- 

 folds (///' and /iff) meet in the middle line. Between the two gills (k) lies the 

 unpaired anal papilla ; on the mantle, are the two prominences representing the 

 rudiments of the fins (cf. Fig. 118, /). 



In the adult, these muscles are attached to the funnel laterally, some of 

 them running further forward to end within the funnel and in its dorsal parts. 

 This is perhaps indicated even in the embryo (Figs. 117 and 118) by the 

 course of the anterior folds, but we have hitherto been unable to make any 

 careful examination of the fate of these raised parts which anteriorly become 

 connected with the posterior funnel-folds, and must therefore refrain from 

 conjectures as to their significance. 



