SlRUCrURE AND DEVELOPMENT OF COELOl'LANA. 45 



the margin of tlie body, often taking a more or less undulating course. 

 Branching and varicose appearance are not uncommon. The fibres are 

 readily distinguished from the muscle-fibres prevailing in the same 

 regions b}' being extremely fine. 



According to Abbott ('07), fairly remarkable nerve-ganglia should 

 be found close to the aboral sense-organ in the interradial regions. 

 However, I could not succeed in finding them in spite of several special 

 attempts. Sometimes I used the wasser-blau-eosin method, which the 

 author recommends very highly, but I could make out nothing like 

 ganglia in those regions. Accordingly, I am inclined to entertain doubt 

 as to the presence of such ganglia as pointed out by him. Certainly, he 

 has given clear figures of the alleged ganglia; further, he has called 

 attention to Korotneff's statements {'S6) which show an allied structure 

 in the same parts in Ctenoplana. Nevertheless, I can not help regarding 

 the alleged ganglia in either case to be muscle-fibres in reality, before 

 some clear evidence for their nervous nature would be presented. The 

 same parts in Coeloplaua are traversed by muscle-fibres very richly and 

 the groups of the fibres give in sections figures somewhat resembling 

 ganglia; they stain with meth}'le-blue very strongh". 



Development. 



The development of Coeloplaua bocki was described briefl}' in my 

 previous paper ('20, a). In the following, somewhat fuller accounts 

 will be given. Kre.mpi' ('20. c, '21) also has given description of 

 the development of Coeloplaua t^onocteiia which he studied in Annam. 

 As he has pointed out, the results of our studies are in almost full 

 agreement. 



In many indi\-iduals of C. bocki, secured during summer or autumn 

 months of 19 18 and 1919, I came across egg-clusters overlain by them 

 (Text-fig. 2). They contained cleaving eggs or cydippid-like embryos of 

 various developmental stages. Further, I could rear up the eggs and the 

 embryos to some advanced stages in the aquarium and fill up most of 

 the gaps existing between the stages obtained. So that, the development 

 of the animal could be followed up to a tolerably satisfactory measure. 



Egg- 

 The eggs, so far as observations in the aquarium have ascertained, 



