DEVELOPMENT OF A MYXOSPORIDIAN 355 



It would be strange indeed, if this method of multiplication 

 is confined to the species under discussion. Erdmann ('11) 

 has described peculiar protoplasmic bodies which sometimes 

 emerge from disintegrating trophozoites of Chloromyxum ley- 

 digi, and which she considers S'egetative reproductive bodies.' 

 These bodies are apparently homologous with the gemmules of 

 S. dimorpha, although Erdmann believes that their function is 

 to provide for reproduction under unfavorable conditions only. 

 This belief is apparently based on the fact that she observed their 

 formation only in trophozoites growing on a gall agar culture 

 medium, or introduced into the digestive tract of the host. 



I have evidence (which will be reserved for a later paper) 

 indicating that a similar method of endogenous budding, result- 

 ing in the formation of gemmules, occurs in a species of Cera- 

 tomyxa found in the gall bladder of a shark, Carcharhinus sp., 

 and also in a Myxosporidian (probably a new genus) occurring 

 in the urinary bladder of the flounder, Paralichthys albiguttus. 



3. Propagative reproduction 



Probably the sole method of propagative reproduction among 

 the Myxosporidia is by the formation of resistant spores which 

 can live for some time outside the body of the host. The proc- 

 ess of sporulation, which is in all cases very complicated, has 

 been studied by a number of investigators. Auerbach ('10) 

 has given a very full review of the work on sporulation, and as 

 the earlier accounts are so evidently erroneous in many respects, 

 it is unnecessary to consider them here in detail. The most com- 

 plete of the earlier accounts is that of Thelohan ('95), accord- 

 ing to whom sporulation begins in Myxobolus by a single nucleus 

 becoming surrounded by a spherical, condensed mass of proto- 

 plasm, which is in turn surrounded by a membrane. The nu- 

 cleus then divides by mitosis until ten nuclei are present in 

 the pansporoblast. The pansporoblast then divides into two 

 parts (sporoblasts), each containing four nuclei. The remain- 

 ing two nuclei remain outside the sporoblasts and gradually 

 disappear. Each sporoblast becomes converted into a spore, 



JOURNAL OF MORPIIOLOGV, VOL. 27, N'O. 2 



