No. 2.] STOLONIZATION IN AUTOLYTUS VARIANS. 275 



The ventral tentacular cirri (v.t.) are much more slender and 

 about one-fourth as long as the dorsal pair. 



The head differs in shape from that of the parent stock in 

 being broad and emarginate in front. Two pairs of eyes are 

 present ; those corresponding to the anterior eyes of the parent 

 stock, being the larger, are placed on the ventral side of the 

 head, so that they are not seen in a dorsal view of the animat. 

 The ventral eyes are considerably larger than the correspond- 

 ing ones of the parent stock, and bear conspicuous lenses which 

 are directed down and outward. The second pair are smaller in 

 size and are placed dorsally and directly over the ventral pair. 

 Small lenses are present and directed upward and forward. A 

 single median tentacle and two pairs of lateral tentacles com- 

 prise the appendages of the head, distinct palps being absent. 

 The median tentacle {d.ni) is about equal in length to the 

 dorsal tentacular cirrus, but is less stout at the base and is 

 always directed backward. The anterior lateral tentacles (a./.) 

 are flattened dorso-ventrally, are very broad at the base, gradu- 

 ally tapering as they curve outward, and end in bifurcated 

 processes which are not unlike dorsal cirri. The position and 

 form of this tentacle have led Malaquin and several other inves- 

 tigators to regard it as being formed by the fusion of the palp 

 with the lateral tentacle, the inner ramus representing the 

 palp, the outer, the anterior lateral tentacle. The posterior 

 lateral tentacles (/./.) are short and straight, inserted anterior 

 to the dorsal eyes and usually directed forward, reaching a 

 little beyond the margin of the head. This pair of tentacles 

 is not represented in the parent stock. The mouth opening of 

 the Polybostricus, as also of the Sacconereis, lies a little ante- 

 rior to the base of the ventral tentacular cirri and is directed 

 downward. 



The Sacconereis of this species (PI, XIII, Fig. 5) is from 3 

 to 4 mm, in length and contains from sixteen to twenty setiger- 

 ous segments. Swimming setae are usually absent from the 

 first two setigerous segments, sometimes only from the first. 



The buccal segment is narrow dorsally ; ventrally, however, 

 it is quite well marked. The dorsal tentacular cirrus is absent, 

 but a small papilla (d.t.) occupying the same position may be 



