ORIGIN AND MORPHOLOGY OF CHLOROPHYLL CORPUSCLES. 245 



as has been killed by glycerine^ or other reagents, often gives 

 the appearance of a uniformly coloured protoplasm, and this 

 has no doubt given rise to the prevalent idea of an absence of 

 definite chlorophyll bodies in certain cases. 



Such chromatophores may be present singly, or in larger 

 numbers in the cell ; their form is very various, but their 

 general form, and their number in the individual cell, are con- 

 stant for any given species. 



The simplest form is that of a small flat disc, of round or 

 irregularly angular outline, as in the Characeae, Siphonese (fig. 

 15), and various other Chlorophycese., &c., and the great 

 majority of the Phoeophycese, also in very many E/hodophycese. 

 Closely connected with this simplest form of chromatophore is 

 that with a more or less lobed margin, while the most varied 

 transitional forms lead to large flat discs with various develop- 

 ment of their contour. The latter form is most common 

 among the Chlorophyceae, and less frequently found among 

 the red and brown Algae, narrow and band-like chromato- 

 phores being more common in these groups. A further devia- 

 tion from this discoid form of the chromatophores is shown in 

 many Chlamydomonads, Volvocineae, Palmellaceae, &c., in 

 which in accordance with the spherical form of the whole cell 

 of these plants, the chromatophore is moulded into a hollow 

 spherical form, while it is strongly thickened in the middle, so 

 that the whole assumes the shape of a watch-glass; sometimes, 

 however, this central thickening is so strong that the chro- 

 matophore has an almost spherical form, with only a slight 

 flat hollowing at one side, as in Pleurococcus, Palmella, 

 Volvox, &c. 



Far more complicated forms result from the formation of 

 narrow bands not at the margin, but on the surface of the 

 discoid chromatophore. Such processes are not uncommonly 

 found as median weals on the inner surface of the chlorophyll 

 bands of Spirogyna, or the plates of Mesocarpus, &c. But 

 where several such weals traverse the chlorophore longitudi- 

 nally, and on both sides of it, a form is attained such as in 

 Micrasterias, while a further development of the same sort is 



VOL. XXIV. NEW SKll. K 



