MUSEUM OF COMPAKATIVE ZOOLOGY. 



105 



that iu Pedicelliua, iu which the metamorphosis of the larva has beeu best 

 studied, the stolon arises from the base of the stalk — that is, at the pole 

 where mouth and anus were first formed — at the pole of invagination. 

 I have shown that this is true for Phylaotolaemata, and probably for 

 Gymuolsemata. 



If the interpretation which I have put on Gymnolsematous ontogeny 



becomes confirmed, the larvae and the budding areas will be homologous 



throughout all Bryozoa. The following diagrams will explain my idea 



of the relation of the different ontogenetic stages in the two groxips. 



Endoprocta. Ectoprocta. 



The left hand vertical series represents stages in the development of 

 Endoprocta ; the right hand one, stages of Ectoprocta. The blastopore (*) 

 is throughout turned upwards in the figures. Stage I. is in both cases a 

 young gastrula. Stage II. is that of the free-swimming larva of Endo- 

 procta. This stage is lost iu the ontogeny of Ectoprocta, in which, by 

 abbreviation of larval life, the free-sw-imming stage corresponds to the 

 condition of the fixed Endoproct after it has undergone its rotation. 

 This stage, or one slightly later, is shown in III. Both larvae are fixed, 

 the Endoproct by the blastoporic, the Ectoproct by the opposite pole. 

 The position of the stolon, or of the first polypide of the colony produced 

 by non-sexual methods, is represented at gm., near the blastoporic pole. 



