152 THE AMPHIOXUS. 



relations of position to notochord and alimentary 

 canal, and their relations to the first mesoblastic 

 somite. I will not describe this here in detail, but 

 merely refer to the plates (Figs. 113, 114, 121, 122, 

 129, 130). 



DEVELOPMENT OF THE CLUB-SHAPED GLAXD. 



We will now observe more closely the development 

 of another organ, which is formed from out of the 

 alimentary canal. This is the peculiar gland which 

 all previous observers had found in the Amphioxus 

 larva, with regard to whose formation, however, we 

 have entirely erroneous statements, and whose 

 structure was hitherto not thoroughly recognised. 



This gland originates through a folding from out 

 of the alimentary canal, in the region of the first 

 myotome. 



In the embryos, even with 9-10 mesoblastic somites, 

 a very shallow and transverse folding of the alimen- 

 tary canal may be recognised in this region (Fig. 50). 

 This advances ventralwards, from the right side wall 

 of the alimentary canal, where it is most sharply 

 marked, and reaches over to the left side wall. In 



