THE MYXOSPOTtlDIA, OR PSOROSPERMS OF FISHES. 



115 



2. Position and f/rotipinf/ of the capfsules. — Coiiipured to these all- 

 iiiiportaut characters, the mere number of the capsules is of minor impor- 

 tauce. For, m)t only does the same genus frequently show 1 or 2, 2 or 

 4, but the number may even vary in the same species, as (apart from 

 the entirely anomalous case of Myxoholu.s ellijjsoides, Avhere " accessory" 

 capsules may develop) My.vidium lieherhilhnii shows sometimes 2 and 

 sometinies 4 cai)sules.^ But Avhat is never varied in the same genus 

 is the topofjrapltio relation of the cai^sules. Thus in Myxoholus, while 

 in number they may be either 2 or 1, they are never arranged otherwise 

 than in one group, or placed otherwise than at the anterior end, and 

 similarly in all the other genera. In Myxidium the capsules are 2 

 or 4, but whether 2 or 4, they are always in two groujis at the right 

 and left extremities of the spore. Also in Cystodiscus they are 2 or 4, 

 but always in two groups, which, however, are probably anterior and 

 posterior in position (see p. 278). 



In the following table I have plotted out the principal characters and 

 indicated their relations to generic lines. 



Comparison of generic characters in the Phmnocystes. 

 ■[X=present; 0=rabseiit; ( ) = less uoual ; — =condition not linown.] 



* From analogy and general similarity of appearance, this genus can hardly be other thanbivalve. 



to. (S.) ohhnacheri. 



X Imperfect. Shell and capsules symmetrical ; sporoplasm unilateral. 



From this table we may conclude that — 



1. Henneguya agrees with Myxoholus in every respect but one, the 

 presence of a tail. (See also p. 206.) 



2. Thelohan's groups, '■^ Myxidiees^^ and " Ghloromyxees,^^ must undergo 

 rearrangement (see table below); for clearly Chloromyxum, Myxosoma, 

 and Sphcerospora form a compact group, with which Myxidium has no 

 character of consequence in common except the absence of a vacuole. 



' Balbiani, 1883, Journ. de Microgr., vii, p. 274, lig. Gig. 



