3i6 THE SPOROZOA 



sch'izogony of Schizocystis given by Leger (see above, p. 191), and it is 

 very possible that the true position of Siedleckia may be found eventually 

 to be in or near the Schizogregarinae. To what extent it is at the same 

 time allied to Amoebidium must remain an open question. 



Genus 3. Toxosporidium, Caullery and Mesnil, 1900, for T. sabellidamm, 

 C. and M., parasite of various Sabellidae (Fabricia sabella, Oria armandi, 

 Amphiglena mediterranea, Jasmineira elegans, and Myxicola dinar densis). 

 This form may conveniently be considered in connection with Siedleckia, 

 although its affinities are extremely doubtful. Its discoverers approximate 

 it provisionally to the coelomic Gregarines. It occurs in the form of 

 motionless crescents lodged principally in the phagocytic cells of the body- 

 cavity of the host. Each crescent has a nucleus containing two large 

 crescent-shaped karyosomes. In the same hosts the intestinal epithelium 

 contains "groups of spherules, which are perhaps the phase of endogenous 

 multiplication of these parasites," the spherules being supposed to fall into 

 the peri-intestinal blood-sinus and develop into the crescents. No other 

 stages are known. 



Genus 4. Joyeuxella, Brasil, 1902, for /. toxoides, Bras., parasite of the 

 intestinal epithelium of Lagis koreni. The youngest stage of the parasite 

 is a crescent-shaped intracellular body containing a nucleus with a large 

 karyosome, and near the nucleus a small body resembling a micronucleus, 

 and sometimes also another one further off. With further growth the 

 nucleus multiplies, and the full-grown crescents have very numerous small 

 nuclei. The body then divides up into numerous small elements. The 

 further development has not been followed, but the epithelium of the 

 same hosts also contains bodies resembling cysts of microgametes. Brasil 

 considers that this form has some points of resemblance to Gonospora, 

 Selenidium, and Toxosporidium ; to Siedleckia, from which it differs in 

 form, immobility, and intracellular habitat ; but that on the whole it 

 shows more affinities with Coccidia than with Gregarines. 



Genus 5. Exosporidium, Sand, 1898, for E. marinum, Sand, an 

 ectoparasite observed, in a single instance, on the leg of a marine Acarus 

 at Eoscoff. The parasite has a general resemblance to Amoebidium, being 

 attached by one extremity of the cylindrical body, which becomes slightly 

 narrower towards the free distal extremity. The dimensions given are 

 193 //. in length by 23 fj. in breadth at the fixed extremity, 17 ft at the 

 free end. The body is limited by a distinct membrane, within which the 

 protoplasm is divisible into (1) an ectoplasmic layer resembling that of 

 Gregarines, clear and free from coarse granulations ; (2) a granular endo- 

 plasm containing six nuclei disposed in a longitudinal series. Two kinds 

 of movements were observed flexions, followed by sudden straightenings, 

 of the whole body, and slow torsions of the free extremity. Sand con- 

 siders this organism to be a Sporozoon, allied to Amoebidium. 



The following genera are of quite uncertain position amongst the 

 Sporozoa, if indeed they are Sporozoa at all : 



Metchnikovella, Caullery and Mesnil, 1897, for certain minute para- 

 sites infesting the endoplasm of certain Gregarines. The first phase of 

 the parasite is a number of small nucleated corpuscles lodged in a vacuole 



