748 



ZOOLOGY 



SECT. 



middle line ; and these, with the posterior folds, go to form the 

 completed funnel together with the "neck-muscles." For a time 



cir.j 



yk.s 



FIG. 660. Two later stages in the development of LoligO, A, from the funnel side. B, obliquely 

 from above. Letters as in preceding figures ; /u. cart, nuchal cartilage (After Korschelt and 

 Heider.) 



B 



LTt 



yk.S 



FIG. 661. Two stages in the development of IiOligO, later than those represented in Fig. M'.H. 

 From the anal or funnel side. Letters as in preceding figure ; in addition, fin, fins. (After 

 Korschelt and Heider.) 



the edges of the two folds which form the funnel remain free :. 

 eventually they coalesce to form a complete tube. 



