No. 2.] STOLONIZATION IN AUTOLYTUS VARIANS. 2S3 



the appearance of a very narrow lighter band of interposed em- 

 bryonic tissue. It is in this tissue that the separation of the 

 stolon from the chain will take place. It becomes plainly visible 

 for the first time between consecutive stolons of this stage of 

 development, and appears most prominently here, being in later 

 stages hidden by the overgrowing head of the succeeding stolon, 

 and also probably because of the structural changes, to which 

 I shall refer later. 



Stolon 3 shows a few more advances in the process of devel- 

 opment which make their appearance in an individual of this 

 size. This stolon consists of eighteen setigerous segments, 

 followed by the anal segment, not shown in this sketch. The 

 anterior segments are somewhat larger than those of the pre- 

 ceding stolon, and the parapodia and dorsal cirri are more 

 prominent and more fully developed, the whole individual pre- 

 senting a larger and more mature appearance. The breadth 

 of the head has increased in conformity with the breadth of 

 the first setigerous segment, and a second pair of eyes (^./.) 

 has appeared, being placed posterior to the first pair and in a 

 line with the insertion of the dorsal median tentacle. These 

 eyes are not so widely separated from one another as are the 

 first pair and are considerably smaller. The arrangements of 

 the eyes on the head of this stolon very closely simulate the 

 position of the eyes on the head of the parent stock, although 

 the shape of the head is decidedly different. The appendages 

 of the head have also increased in size ; the dorsal median ten- 

 tacle has increased by about the width of two segments and 

 reaches as far back as the third setigerous segment. The two 

 anterior lateral tentacles, besides having increased in length, 

 also show indications of branching by the appearance of a small 

 bud on the median side of each tentacle. The bifid tentacle 

 being characteristic of a male stolon, it is possible even at this 

 stage of development to distinguish the sex of the stolon and 

 hence of the chain. In a dorsal view of this stolon the outline 

 of the buccal segment is not more visible than in the preceding 

 stolon, and were it not for the projection of the dorsal tentacu- 

 lar cirri {d.t) evidence of the existence of this region would be 

 wanting. Laterally the buccal segment has attained a consid- 



