"250 s. GOTO; 



junction of the œsopbagus und stomach. I could observe nothing that 

 suggested any abnormality in this specimen, nor anything to show 

 that tliis division was due to mechanical injury. It seems to me 

 therefore that we must admit the occurrence, in some cases, presumably 

 few, of such a variation from the rule. There is nothing that requires 

 any special description connected with the atrophy of the protostome ; 

 the portion connected with the mouth, that was cut off from the rest 

 being again evaginated and forming a portion of the oral disc, 

 while the portion connected with the stomach becomes thicker and 

 shorter and forms the definitive œsophngus. During this change the 

 cardiac valve of the stomach becomes less distinct and finally dis- 

 appears altogether (cf. among others, Figs. 9, 10, PI. XIX, & Fig. 39, 

 PI. XXIII). The metastome is formed by the coalescence of the oesoph- 

 agus with the ectoderm of the oral side and its subsequent breaking 

 through. This takes place in stage H (Fig. 10), and is represented in 

 section in Fig. 36. 



Protoproct. — During the passage from a fully developed brachio- 

 laria to the transforming stage the larval anus is considerably shifted 

 to the right side of the body, and in a stage intermediate between 

 stages F and Gr, it lies just beneath the aboral disc between arms I and 

 II, nearer the latter (Fig. 40, PI. XXIII). [For the numbering of the 

 arms see figures on Pi. XIX.] It begins to atrophy at this stage, the 

 process being inaugurated by a fusion of the ectoderm forming the 

 rim of the anus (Fig. o2, PI. XXII). The portion of the intestine ad- 

 joining the anus is then partly constricted oif from the rest, nnd sub- 

 sequently undergoes histolysis. In Fig. 32 one can see this process 

 going on ; and the character of the nuclei of the epithelium, the presence 

 of numerous amœbocytes and of a finely granular substance in the 

 vicinity, and the general indistinctness of the surfaces of the epithelium 

 all prove that this portion is actively undergoing disintegration. 



