ASCIDIACEA TRANSVERSE FISSION. 



453 



elongated, branched post-abdomen of many Polyclinidae (e.g., Circin- 

 alium), part of which creeps horizontally along the substratum, is 

 remarkably like the stolon of Glavelina. These two methods of 

 reproduction are thus connected with each other by transitional 

 forms. 



FIG. 227. A, youug Amaroucium before the commencement of asexual reproduction ; 

 H. Ainarouciwn with segmented post-abdomen (after KOWALEVSKY). a, thorax; 

 b, abdomen ; c, post-abdomen ; h, heart ; s, partition-wall ; s', anterior part of the 

 partition-wall ; .-/;, ?/, separated portions of the post-abdomen ; k, anterior -swollen 

 i-iid of the partition-wall in the posterior separated portion. 



The commencement of asexual reproduction in the post-abdomen 

 of Amaroucium is marked by its elongation and the abstriction of 

 its soft part from the point of attachment to the rest of the body. 

 The heart continues to beat after the separation of the post-abdomen 

 from the abdomen is accomplished. Soon after, the post-abdomen 

 (Fiu. 'I'll B] breaks up, through transverse fission, into a varying 



