4 2 Chtorocystis SarcopJiyci. 



generally completely fill the cell-cavity (plate XIL, fig. n). I have 

 found the number of spores in many cases to exceed one hundred, the 

 number, however, varying according to the size of the cell containing 

 them. Even in the spirit material on which I have worked there often 

 remains a decided green colouration of the contents of a cell before spore- 

 formation ; on the other hand, there is always a marked diminution of 

 colour after spore-formation has occurred. Besides these two prevailing 

 conditions of the contents of an endophytic cell, there remains yet a 

 third condition, the meaning of which I shall have to discuss later. In 

 this the protoplasm is segmented into portions of considerably larger size 

 than the small spores which I have described (plate XII., fig. 10). The 

 segmentation appears to proceed simultaneously throughout the whole 

 protoplasm, and the resulting segments, though fairly regular in size, are 

 not very uniform in shape ; the green colouration is as well marked as it 

 is before such segmentation has occurred. 



Of the endophytic and unicellular Algae hitherto described, the 

 species to which I believe this endophyte of SarcopJiycns to be the most 

 nearly allied is CJilorocJiytriuni incliiswu, described by Kjellman*, in the 

 fronds of the Floridean SarcopJiyllis arctica. The spore-containing cells 

 which I have described, though considerably smaller in size, yet bear a 

 most striking resemblance to those figured by Kjellman. Kjellman refers 

 his species to the genus Cklorockytrium, but it seems probable that 

 it, together with other marine forms, should be placed in the genus 

 CJilorocystis of Reinhard, and I venture to think that, so far as can be 

 judged without knowing the whole life-history, the species occurring in 

 SarcopJiycns belongs to the same genus, and I have therefore named it 

 CJilorocystis SarcopJiyci. 



The genus CJilorocystis was founded by Reinhardf on ClilorocJiytrmm 

 CoJmii, described by Dr. Wright* as occurring in several species of 

 ScJiizonema, in PolysipJwnia urccolatn and other marine Algse. 



The chief point of distinction between the two genera is that in CJiloro- 

 cJiytrinui spore-formation occurs by repeated division of the protoplasm 

 into two, the resulting portions being separated from each other by a 

 cell-membrane, while in CJilorocystis the spores arise by free-cell-formation. 



The characteristics of the genus CJilorocystis are given as follows in 

 De Toni's Sylloge Algarum (vol. i., p. 637) : ' Cellulae sphaericae, tuber- 

 culo lateral! (ut in CJdorocJiytrio} instructae, chlorophora perforata varie 



* Alga; of the Arctic Sea, p. 320, tab. 31. 



t Proc. Neu> Russian Society of Naturalists, vol. ix., p. 214. 



\ Trans, of Royal Irish Academy, vol. xxvi., p. 355. 



