THI5 BIONOMICS OF CONVOLUTA KOSCOFFENSIS. 393 



much variation in the form of its chloroplasts and inclusions. 

 Changes in the chloroplasts of diatoms and Flagellata, for 

 example, accompany a change from holophytic to saprophytic 

 existence (Matruchot and Molliard, 1900; Karsten, 1902; 

 Dangeard, 1902). Hence the irregularities in the development 

 of the colourless cells to the green cells within the body of 

 Convoluta cease, with deeper insight into the complexity 

 of the process, to be a matter of surprise. 



The influence of prolonged darkness on the colourless cells 

 remains to be considered. We have seen that in darkness, as 

 in light, these elements may make their appearance in larval 

 Convoluta. In light a more or less gradual development 

 of chlorophyll takes place. In darkness this is not the case, 

 though, as we have just mentioned, chlorophyll once well 

 established is not destroyed by absence of light. 



A number of young Convoluta were reared from the 

 capsule in sea water with their parents, and, after acquiring a 

 supply of colourless cells and a few green cells, were trans- 

 ferred to jars of sea water placed in darkness. The transfer 

 was made on August 24th, the Convoluta being then two to 

 three days old. On September 4th — that is, after an interval of 

 eleven days — they were examined. Some contained several 

 green cells. In others the green colour was replaced by 

 yellow diffuse pigment, and in these cases numerous irregular 

 inclusions and fine fatty granules were also present. In 

 these latter cases the yellow chlorophyll occupied only a small 

 portion of the periphery of the cell. In yet other examples 

 the contents of the cells Avere composed of yellowish globules 

 and of finely divided fat. These specimens form a series 

 (see fig. G a) leading from typical green cells to mere aggre- 

 gates of fat staining deeply with osmic acid. There can be 

 no doubt that in this case we see the degeneration of the 

 chromatophores under the influence of darkness combined 

 with starvation. 



Having shown that high light-intensity favours the develop- 

 ment of chlorophyll in the colourless cells, and that darkness 

 with, presumably, concomitant starvation causes degeneration 



