272 MENSCH. [Vol. XVI. 



large number of red spots extending along the walls of the 

 alimentary canal through its entire length, but particularly 

 numerous in the region of the oesophagus and in the posterior 

 and more mature stolons. The free-swimming stolons of this 

 variety have a distinctly light red color and are considerably 

 larger than those of the other variety. The other variety has 

 a greenish hue, with few or no red spots along the alimentary 

 canal, and is somewhat smaller and more slender. Intermediate 

 forms are, however, frequently found, and the distinction between 

 the two varieties is not so well marked in the parent stock as 

 it is in the mature stolons. The free-swimming stolons of this 

 variety, besides being smaller in size, are light green in color 

 and somewhat iridescent. They differ very little in size from 

 the free-swimming stolons of A. cornutus, but the male stolons 

 can readily be distinguished from these by the fact that the 

 Polybostricus of A. varians has swimming setae wanting on the 

 three anterior parapodia, while in A. cornutus they are wanting 

 on the six anterior pairs. The Sacconereis of either species can 

 also be readily distinguished by the characters common to each 

 mode of stolonizatipn. 



The parent stock of Autolytus varians (PI. XIII, Fig. i) con- 

 sists of a series of setigerous segments varying in number from 

 nineteen to as many as fifty-eight, the larger and older individ- 

 uals always containing the larger number of segments. Ante- 

 rior to the first setigerous segment is a segment (PI. XIII, 

 Fig. 2, b.s^ called the buccal or tentacular segment, in which 

 parapodia are absent ; but instead of these are present two pairs 

 of cirri, called the dorsal {d.t.) and ventral (v.t}) tentacular cirri 

 respectively. The dorsal tentacular cirri are longer and con- 

 siderably thicker than the ventral pair, which are short and 

 slender and more like the dorsal cirri of a setigerous segment. 

 The segment itself is usually considerably narrower than the 

 succeeding setigerous segment. Anterior to the buccal seg- 

 ment is the head, which consists in this species of a rounded 

 lobe with two pairs of eyes, an anterior larger and posterior 

 smaller pair, bearing a single dorsal median {d.m.) and a pair 

 of lateral tentacles (/.). A pair of rudimentary palps form the 

 ventral appendages of this lobe. 



