426 THE PROTOZOA 



Under the generic name Microklossia, Krassiltschik has described 

 certain cell-parasites of caterpillars, which appear to belong to the Neo- 

 sporidia, though it is not possible to assign the genus to a definite position, 

 since the structure of the spores has not been made out, and the account 

 given of the life -cycle requires revision. According to Krassiltschik, the cycle 

 begins with non-sexual schizogony ; the nucleus of the schizont divides into 

 four or eight nuclei, and as many merozoites are produced within the body 

 of the schizont. Schizogony is succeeded by formation of " macronts " and 

 " micronts " which give rise to gametes ; the macront by a process of fission 

 similar to the schizogony produces four to eight macrogametes, while the 

 micront produces in a similar way two, four, or eight, microgametes. The 

 nucleus of the macrogamete divides to form two reduction-nuclei. The 

 microgamete attaches itself to one pole of the macrogamete, and its nucleus 

 passes over into the cytoplasm of the latter and fuses with the female pro- 

 nucleus. In the zygote the synkaryon buds off daughter-nuclei, round 

 which the cytoplasm of the zygote is condensed to form internal buds " pro- 

 toblasts." The protoblasts are set free, and produce in their turn " deuto- 

 blasts," which are set free, become amoeba-like, multiply in the blood of the 

 insect, and infect the tissues and organs of the host, especially the fat-body 

 and the wall of the digestive tract. In the fat-body the deutoblasts produce 

 a generation of " tritoblasts " which multiply actively and spread amongst 

 the tissue. From the tritoblasts arise finally a generation of " teloblasts," 

 which divide each into a rosette of small cells, the definitive sporo blasts, 

 round a central residual mass. Each sporoblast produces a spore, a smooth, 

 strongly refractile body, ellipsoidal or egg-shaped, in which no details of 

 structure could be made out. The spores appear to be produced in the wall 

 of the digestive tract, whence they are set free with the faeces. The concluding 

 phases suggest a Nosema-type, but the earlier part of the life-cycle, if correctly 

 described, appears to be a type sui generis. 



Under the name Lymphocystis johnstonei, Woodcock (824) described a 

 parasite of plaice and flounders, which forms conspicuous cysts in the lymph- 

 spaces of the skin and mesentery. Each cyst (Fig. 178) contains a single 

 parasite, which may attain 1 '5 millimetres in diameter, and shows a remarkable 

 structure. The body is enclosed by a thick, structureless membrane, and 

 contains at the centre a very large nucleus, irregular in shape, staining feebly, 

 and containing a number of karyosomes in a faintly- staining reticulum. 

 Surrounding the nucleus is a chromidial network forming a ring or zone of 

 considerable thickness, filling the greater part of the cytoplasm between the 

 nucleus and the envelope. The outermost zone of the chromidial net may 

 contain a series of small, clear " spherules." 



According to Awerinzew (815 and 816), the youngest stages of Lymphocystis 

 are minute cells with a single nucleus which grow very rapidly, and as they 

 do so the chromatin passes out of the nucleus to form the chromidial ring. 

 The spherules are masses of plastin which separate from the chromidial net. 

 From the chromidia secondary nuclei are formed, round which a portion of 

 the cytoplasm is cut off to form small cells, termed by Awerinzew " secondary 

 amceboids," and compared by him to the sporonts of Glugea. Within the 

 secondary amceboids spores are formed, of which, however, the structure 

 has not been made out clearly. In teased-up preparations of Lymphocystis, 

 Awerinzew found spores similar to those of Henneguya, and proposed to place 

 the parasite in that genus. He has now become doubtful, however, whether 

 the Henneguya-spores belong to the Lymphocystis or to a distinct parasite, 

 since he was unable to demonstrate a similar structure in the spores found 

 in the secondary amoeboids. Awerinzew is of opinion, nevertheless, that 

 Lymphocystis should be referred to the Cnidosporidia, but this form requires 

 further investigation. 



Toxocystis homari, Leger and Duboscq (646), is a parasite of the posterior 

 intestinal caecum of lobsters. In appearance it resembles a haemogregarine, 

 motionless, with granular cytoplasm and a small karyosomatic nucleus at 

 the middle of the body ; there are also usually two, sometimes one, " para- 



