OBSERVATIONS ON THE GREGABINES OF HOLOTHUEIANS. 291 



I have been able to make them out, of this Gregarine, for 

 which, on account of the irregular form of the adult, I propose 

 the name — 



Gregarina irregularis, n. sp. 



Gregariues of relatively large size (about '5 mm. in length) 

 and of extremely irregular form. The body consists of opaque 

 coarsely granular protoplasm, limited by a distinct cuticle, 

 and containing two large nuclei, each floating separately in a 

 clear space free from granules. The nucleus has a distinct 

 membrane and a single large nucleolus of peculiar vacuolated 

 structure floating in a nuclear fluid. After encystment the 

 protoplasm segments and is entirely used up to form spherical 

 sporoblasts, each of which develops into an egg-shaped spore 

 with a funnel-like expansion of the cuticle at the narrow end. 

 The nucleus of the sporoblasts divides into eight nuclei, which 

 elongate and acquire at one end a flame-like tail, at the other 

 end (?) a minute conical point. Thus are formed the eight 

 sporozoites, which are embedded in a coarsely granular " nojau 

 de reliquat," and are typically arranged in two rows of four, 

 the tail of each sporozoite being parallel to the long axis of the 

 spore and pointing away from the infundibular end of the 

 spore. 



Habitat. — Blood-vessels of Holothuria at Plymouth. 

 The adult form lies free in the lumens of the blood-vessels, 

 but the cysts evaginate the wall of the vessel to form a stalked 

 vesicle. 



We shall now consider the Gregarine of Holothuria tubu- 

 losa, the Gregarinse holothurise of Anton Schneider. In 

 the specimens of H. tubulosa examined by me at Naples I 

 found the adult binucleated form occurring as little stalked 

 vesicles attached to the blood-vessels, often in great abun- 

 dance. In one specimen in particular there must have been 

 thousands, mostly attached to the dorsal blood-vessel of the 

 intestine, and easily seen with the naked eye. In fig. 19 I 

 have represented some of the vesicles as they appeared in the 



