Dr. R. Greeff on Autolytus prolifer. 181 



The specific characters* of Autolytus prolifer are in many- 

 respects difficult to fix ; thus, as a matter of course, we must 

 give up even an approximate determination of the length or 

 number of segments of the primary individuals, since these 

 characters, as may be easily seen, vary greatly in consequence 

 of prolification. The smallest primary individual engaged 

 in prolification, observed by me, measured 2 millims. to the 

 youngest bud offspring, and contained to the same point four- 

 teen segments, with the exception of the head. The largest 

 primary animal engaged in prolification, on the other hand, 

 measm-ed more than twice as much as the former, and con- 

 tained thirty -nine segments to the commencement of the bud 

 offspring. The fully developed animal before the commence- 

 ment of prolification must therefore have been a good deal 

 longer. I think, however, that the length of Autolytus pro- 

 lifer will not usually much exceed 2 lines, as stated also by 

 Krohn. 



The head presents no indication of lobe-formation on its 

 upper surface ; but on the lower surface there is a narrow, 

 median, longitudinal, impressed line, which divides and widens 

 in a curve to right and left posteriorly, and thus forms the 

 anterior buccal angle, so that the hinder parts of the head- 

 lobes at the same time form the anterior buccal lobes or 

 lips. Directly opposite to this anterior buccal angle there is 

 a posterior one, the arms of which join those of the anterior 

 angle, so that by this means a lateral angle is also pro- 

 duced on each side. The buccal orifice has a quadrangular 

 form, bounded by curved lines with their convexity in- 

 wards. ' On its upper surface the head bears four reddish- 

 brown eyes, furnished with lenses, the position of which, 

 however, varies according as the two on each side are more or 

 less approximated to or removed from each other, as shown 

 in our figures. Usually they group themselves in a quadran- 

 gle, the anterior pair being further apart than the second (pos- 

 terior) pair. The three cephalic tentacles occm* of very different 

 sizes in different individuals ; generally, however, they do not 

 attain the very considerable length represented in fig. 1, but 

 are much shorter. They are then capable of very lively move- 

 ment, are constantly waved to and fro, and pushed through 

 each other, feeling about, and, when thus employed, show the 

 peculiar transversely furrowed and twisted appearance already 



* I shall refer only to the specific characters of the primary individuals 

 of Autoh/tus prolifer, as good and perfectly satisfactoiy descriptions of the 

 male and female hud offspring {Sacconereis and Polybostrichus) have heen 

 given by the authors already cited, and to these I can add nothing essen- 

 tial. 



