1912.] On a Gregarine present in Mid-Gut of Ceratophylli. 33 



cephaline Eugregarines, which have spores unarmed with spines." He 

 proposes to name the Gregarine Agrippina bona, and to refer it to a new 

 family — the Agrippinidae. As this Gregarine exhibits features so striking 

 as to require for its reception a new family, it is evidently different from 

 that described below, for the latter is referable to a well-known genus, 

 Steinina. Agrippina bona differs from the new species of Steinina described 

 in the following pages, not only in certain points of structure, but in being 

 restricted to the larval gut and faeces, for, in S. rotundata, the trophozoites, 

 although occurring in the larva, reach their full size only in the adult flea. 



Description of Steinina rotundata, and of its Life-History. 



The life-cycle of this Gregarine has been traced almost exclusively in 

 specimens of Ceratoph/yllus styx. The early trophic phases of the Gregarine 

 occur in the larvae of this flea, and are either attached to the wall or lie 

 free in the lumen of the mid-gut. We have carefully examined the freshly 

 dissected mid-gut, and also serial sections of the gut of many infected 

 larvae and adults, but we have not been able to identify an intra-cellular 

 phase of the Gregarine. This stage, if it exists, will be extremely difficult 

 to recognise with certainty, owing to the close resemblance between the 

 young Gregarines and the smaller cells about the bases of the gastral 

 epithelium, especially in the neighbourhood of the numerous crypts of 

 regeneration. If there be an intra-cellular stage, it is of brief duration only, 

 for we have observed a number of very young, ovoid trophozoites, 10 /j, long 

 and 5 /u, broad,* attached by their narrower ends to the epithelial cells and 

 hanging into the lumen of the mid -gut (Plate 1, fig. 1). 



Average specimens of the Gregarine, from the mid-gut of young adult 

 fleas, are 45 to 70 /u. long and 30 to 50 /j. broad, but, when full grown, the 

 parasite attains a length of 180 /x and a breadth of 70 to 80 /a. It is usually 

 differentiated into three regions — epimerite, protomerite, and deutomerite. 



The epimerite varies considerably in shape. It often has the form of a 

 blunt and flattened cone (figs. 2a, 3, 5, 6), on the apex of which a small 

 pointed process may be present (fig. 3). In some specimens the epimerite is 

 discoidal or saucer-shaped (fig. 4), its edge being slightly upturned (that is, 

 away from the protomerite). The margin of the epimerite is rarely entire ; 

 sometimes it is lobate, but more usually it is fringed with short processes, 

 rounded or pointed at their tips. These processes are, in some specimens, 

 placed at almost regular intervals and form a single series, while in others 

 they are less evenly arranged, and may be in two or three irregular rows 

 (figs. 2, 4, 5, 6). 



* The sporozoite is about 10 /x long and 1*5-2 p broad (see p. 36). 



VOL. LXXXVI. — B. D 



