258 



EDWIN S. GOODKIUH. 



homologous vvilh the first segment or peristomium of Annelids. 

 Haider has further suggested that the two small processes 

 found in front of the head^ near the median line in the embryo, 

 represent the prostomial tentacles. 



Fig. 6. 



a-nt 



Diagrammatic plan of the anterior segments of the Peripatoidea. Ant. 

 Antenna. Md. Mandible. O.P. Oral papilla. P. Protocerebrum. 

 D. Deutocerebrum. Other letters as in Figs. 1 and 2. 



The study of the development of the brain in Peripatus 

 confirms the conclusions derived from that of the mesoblastic 

 structures. It is formed by the fusion of two pairs of gan- 

 glionic masses derived from the first two segments. Whether 

 the archicerebrum is still to be distinguished, perhaps in the 

 median anterior region, in connection with the pair of small 

 processes mentioned above, is a question which remains to be 

 solved, and requires a renewed investigation. 



The first and largest segment of the brain, which supplies 

 the eyes and antennse, is developed from the ectoderm of the 

 large procephalic lobes (first metamere) . The process is aided 

 by the formation of a crescentic pit, a fold of the surface on 

 either side. The second segment of the brain supplying the 

 mandibles is smaller. The oral papillae are innervated from 

 the ventral nerve-cord. 



We conclude, then, that in Peripatus the first segment has 

 become much enlarged in development, and that the mouth 



