Chaetopelt Idacese 



207 



destitute of mucus (Gk. Pringsheimii). They are approximately spherical 

 with a small conical sheath at the dorsal pole through which passes a long 

 and delicate bristle. The fact that the conical projection is actually a sheath 

 is very difficult to detect owing to the extreme fineness of the lumen. In 

 Dicoleon, in which the cells are similar to those of Chtvtosphteridiuin, there is 

 a double sheath at the base of the bristle, a longer inner sheath growing out 

 of a shorter external sheath. In Conochtete (fig. 136 D) the cells possess 

 several bristles, each of which has a thick, more or less gelatinous, basal 

 sheath. In Polychtetophora (W. & G. S. W., '03) the cells are loosely aggre- 

 gated, or from 6 to 8 of them may form an irregular chain. Each cell 

 has a very thick lamellate wall and is furnished with 8 12 long flexuosc 



Fig. 135. A D, Chsetopeltis minor Mobius. A represents a complete colony, x 550 ; />', two 

 cells showing the chromatophores and nucleus, x 700 ; C, gamete, x 950 ; D, fusion of 

 gametes, x950. E and F, zoogoniclia of Ch. orbicular is Berth, x 540. E, zoogonidia not 

 yet escaped from the surrounding vesicle; F, free zoogonidium. (A D, after Mobius ; E and 

 F, after Berthold, from Wille.) 



bristles entirely destitute of a sheath. In Oligochastophora the cell- wall is 

 quite thin and there are 2 4 unsheathed bristles arising from the dorsal 

 surface (fig. 136 E I}. 



In all these Algae the cells possess a parietal chloroplast (sometimes two 

 in Gonochsete) which in Gh&topeltis is often much lobed and perforated. There 

 is usually a single pyrenoid, and Gonochxte comosa may store oil as a reserve 

 (fig. 136 Do). 



Multiplication of the cells occurs by simple division which in Ch&tosph&- 

 ridium is transverse, the lower cell slipping out from under the upper one 

 and at once developing a sheathed bristle. 



