600 EGBERT SOHAfiFF. 



The only sensory organs are two small ciliated pitSj one on 

 each side of the cerebral ganglion. They are not very con- 

 spicuous, and may quite easily be overlooked. At any rate 

 they are very much smaller than those indicated in Claparede's^ 

 figure of Ct. pardalis. 



Fissiparous Eeproduction. — It has been mentioned 

 that no traces of reproductive organs could be discovered, but 

 many of the animals kept were either young ones or were just 

 undergoing division. A lengthy report of the division of 

 Ctenodrilus pardalis has been published by Kennel.^ The 

 general plan of the division in Ct. parvulus is the same as that 

 in Ct. pardalis. The want of sufficient material prevented me 

 from investigating the histological changes going on during the 

 act of fissiparous reproduction. Hence I will merely state the 

 general characters as far as I made them out, and which agree 

 with those reported by Kennel as occurring in Ct. pardalis. 

 At the same time it will not be out of place to give a short sum- 

 mary of the division in Ct. monostylosin comparison with 

 that of the two other forms. A few diagrammatic drawings 

 (figs. 3 and 4) will help to make the statements clearer. 



We find a peculiar, but at any rate primitive, condition with 

 regard to the division of Ct. pardalis and parvulus. The 

 great characteristic of these two Annelids is that almost every 

 segment becomes a zooid which rapidly develops into the multi- 

 segmented form. This is brought about in the following manner : 

 — A bud appears between two segments, and, in distinction to 

 Naids and kindred forms, the buds are produced in the same 

 order as new segments are, viz. from before backward (fig. 3, b). 

 In Naids the production of buds takes place in a similar way to 

 that of the tapeworm, a condition which has been termed 

 " strobilation." Hence Semper' s^ " proglottidentheorie," which 

 he thought was applicable to all Annelids, does not hold good 

 in the case of Ctenodrilus. 



In order to make the terms " strobilation" and " segmenta- 



1 Claparede, loc. cit., pi. xv, fig. 28 



2 Kennel, loc. cit., p. 395. 

 ^ Semper, loc. cit., p. 290. 



