194 SPOEOZOA. 



granules, and secretion of a firm cuticle, into the adult Gregarines. 

 With this agree the observations of A. Schmidt,^ who found the first 

 stages olMonocystis luinbrici as extremely small, transparent,membrane- 

 less creatures within the spermatic vesicles of the host, and who also 



Fig. 97. — PseudonavicellsB with germinal rods in their interior; A-C, oi Monccystis 

 agilis; D and E, of Urospora nemertidis; F, of Gonospora terehellm (after Aimfe Schneider). 



attempted to follow their further development. Such a Gregarine is 

 sometimes so small that it hardly attains a third of ■ the diameter of 

 the vesicle, but is in other cases so large as completely to fill it, and 

 even to distend it beyond its usual dimensions.^ The sperm cells, 

 which are situated outside the infected vesicles, have obviously a some- 

 what abnormal development in consequence of parasitism, showing, 

 instead of long threads, a short tufted fringe, which persists for a 

 while on the periphery of the young Gregarine, ^ and is only thrown 

 off after they creep out. 



According to the younger van Beneden,^ the development of Gre- 

 garina gigantea, which lives in the intestine of the lobster, and some- 

 times attains a length of 16 mm., is somewhat less direct. Instead 

 of passing directly into the Gregarine form, the amce.boid mobile stage 

 produces two long bud-like processes, which then pass into Gre- 

 garine forms, which are at first destitute of a nucleus. 



We must leave it to the future to decide between these contradic- 

 tory opinions,^ and will only further state that, according to Schneider, 

 there are also Gregarines whose Pseudonavicellfe, instead of the 



^ " Beitrag zur Kenntniss der Gregarinen und deren Entwickelung," AWiandl. d. 

 Senkenherg. Gesellsch., Bd. i., p. 168 et seq., 1864. 



2 See the confirmatory researches of Lieberkuhn, MUller' s Archiv f. Anat. u. Physiol, 

 p. 509, 1865. 



" Such structures have given occasion to the opinion that there were (in the earth- 

 worm) Gregarince provided with bristles. 



* "Recherches sur 1' 6volution des Griigarines, " BuU. Acad. roy. Bclg., t. xxxi., 1871. 

 [Translation, Quart. Journ. Min: Sci., N. S., vol. xi., p. 242, 1871 ; also Ann. Mag. Nat. 

 Hist., ser. 4, vol. x., p. 309, 1872.— W. E. H.] 



^ [The number of these rival theories has recently been increased by Ruschhaupt 

 (Jenaisoh. Zeitschr., Bd. xviii., p. 713, 1885), who does not regard the sickle-shaped bodies 

 in the Pseudonavioellue of the Gregarines as true nuclei, but rather considers that the 

 young Gregarines arise froi£)j||g^g^afoyii^;gJ^^(JfiS@donavicell£e.— R. L.] 



