224 CONVOLUTA. ROSCOFFENSIS- 



covered with very closely-set cilia. A thin epidermal layer is 

 present which in section shows peculiar peg-like projections inter- 

 nally. These projections are evidently connected with a cross-set 

 system of striae on the outside of the animal which can be seen in 

 tangential sections. These projections are. apparently, structure- 

 less and probably represent degenerate muscle fibres. In any 

 case the striae are probably connected with the retractivity of the 

 animal, as in retracted specimens the projections appear much 

 thicker. The main body of the animal appears to be composed of 

 very minute celled parenchyma with many spaces. Amongst 

 these cells are a few larger cells each with a big pyrenoid. These 

 are probably the algal cells of Prof. Keeble, which in the European 

 species are in greater number and arranged in longitudinal rows, 

 and to which the green colour of the animal is due. In the Natal 

 species the green colour is distributed throughout the small-celled 

 parenchyma, together with a large number of darker green 

 bodies, which may be either degenerate algal cells or free chloro- 

 phvll grains. The small cells have a stainable body in them but 

 whether it is a nucleus or pyrenoid I have been unable to decide. 

 In fact in microtome sections I have been unable to get any 

 nuclear staining at all. The small cells are about 5 microns in 

 size, the green grains from 5 to 10 microns, and the large pyre- 

 noid cells are from 25 to 30 microns. I never found any evidence 

 of the animal taking in any solid food particles. 



The reproduction is the most peculiar feature of the animal. 

 After repeated observations I could find no signs of any sexual 

 organs either in the living animal or in microtome sections. 

 Whether sexual reproduction has been discarded altogether it is, 

 of course, difficult to say, but in any case there is a prolific means 

 of asexual reproduction which. I believe, has not previously been 

 recorded, that is. by the severance of parts of the animal, each 

 part being able to form itself into a new animal. This severance 

 may be due to accident such as being dashed against the sand, 

 stones, etc.. in which case the delicate animal comes oft badly, but 

 even the smallest pieces appear able to regenerate. I have divided 

 a single animal into four parts, and after about two hours each 

 part had assumed the elongate ribbon shape of a mature animal, 

 swimming about the whole time. This method of reproduction by 

 the regeneration of parts is of course well known in many animals, 

 such as Hydra, but it is only resorted to in case of accident. The 

 animals concerned cannot be said to reproduce by this method. 

 In the case of Convoluta, however, the delicate nature of the 

 animal is one of its peculiar features, the slightest touch causing it 

 to break or become damaged. In many cases the animal actually 

 puts out protuberances which gradually elongate, and then 

 become separate. This process takes only a short time — about an 

 hour to complete, so that this is hardly a case of budding in so 

 far as the protrusions are not formed by growth. 



I hardly think that the features here described are sufficient 

 to characterise the animal as a new species. It is probably a 

 degenerate form or a variety of the European species. 



