No. 612] MYXOSPORIDIAN LIFE CYCLE 729 



tain restrictions by Mercier and Schroeder. This cell 

 couple {A2 and Bo) should be called envelope cells or 

 envelope cells nuclei when they do not fulfill their des- 

 tin (Schroeder, probably Mercier). Even in those cases 

 in which a pansporoblast membrane had not been dis- 

 covered it might have been either overlooked or have 

 been in evidence at the. beginning of pansporoblast 

 formation before the valves of each single spore had 

 been developed. Later these take up the function of the 

 Hiillzellen which make their retrogressive development 

 plausible. These Hiillzellenkerne are neither Kestkerne, 

 nor reduction nuclei, nor somative residual nuclei. The 

 term for residual nuclei of somatic nature (see definition, 

 p. 679) has already been disposed of in monosporous and 

 disporous forms and must be used in the same way in 

 polysporous forms. In all forms which are polysporous 

 and have many singly developing spores, the whole vege- 

 tative body which is not used up in spore formation has 

 somatic "restkerne" or residual nuclei. As I pointed out 

 in Chloromyxum leydigi the vegetative animal may die 

 after spore formation together with the ' ' restkerne. " In 

 this form the vegetative animal may prolong its life by 

 forming internal buds, if it has reached a considerable 

 size before and during spore formation. In all poly- 

 sporous forms with pansporoblast, i. e., the disporoblastic 

 forms, we have to be verj^ careful when applying the name 

 of somatic residual nuclei. In those species which are not 

 tissue parasites and sometimes have cystlike formations 

 which are surrounded by gelatinous envelopes, we may 

 find somatic residual nuclei, because it seems improbable 

 that the whole vegetative body is used up for spore for- 

 mation. I believe this to be the case in Spliceromyxum 

 sabrazesi and SpluBrospora caudata. Where no residual 

 vegetative nuclei were observed, the investigators may 

 not have studied the whole animal, but only the propa- 

 gative parts of it which have left the vegetative body 

 (Parisi, Fig. 3). Keeping this point in mind, later in- 

 vestigators may discover somatic residual nuclei in de- 



