266 EDWIN S. GOODETCH. 



less some evidence for this interpretation is afforded by the 

 cases brought forward by A. Milne-Edwards of a Palinurus 

 (12), and by Hofer (4) of an Astacus, in which the eye-stalk 

 on one side was produced into a jointed flagellum ; also by 

 some recent experiments of Dr. Herbst, who, having cut off 

 the eyes of Palsemon, finds that jointed antenna-like append- 

 ages are regenerated in their stead (2). 



The prostomium itself may have to be sought forin the median 

 anterior region in front of the procephalic lobes. It has been 

 suggested that the median eye and little frontal processes of 

 the Nauplius larva represent prostomial sense-organs, and it 

 is possible that the anterior region of the brain in connection 

 with these represents the archicerebrum. 



In the foregoing pages the view that the procephalic lobes 

 are homologous throughout the Arthropoda, and represent 

 the peristomial segment of Annelids, has been consistently 

 favoured, not because this interpretation can be considered as 

 firmly established, but from a conviction that the best way of 

 presenting the problem is to uphold a definite theory. Thus 

 both the weakness and the strength of the position become 

 clearer. It is quite plain, however, that much evidence is still 

 needed bearing especially on the presence of distinct meso- 

 blastic somites in the procephalic region in several groups, and 

 on the possibility of distinguishing the true prostomium and 

 archicerebrum in the Arthropoda. 



