THE NEOSPORIDIA 409 



SUBORDER II. : POLYSPOREA. Numerous spores formed in the plasmodium. 

 The greatest diameter of the spore lies in the sutural plane. 



Three families : (1) Myxobolfdce, with two polar capsules (sometimes reduced 

 to one), and with a peculiar vacuole, which stains with iodine, in the amoebula. 

 Typically tissue-parasites of fishes ; principal genera Myxobolus, with round 

 or oval spores, and Henntguya, with tail-like processes to the spore. 



(2) Myxidiidce ; spores with two polar capsules, no iodinophilous vacuole ; 

 typically " free " (i.e., ccelozoic) parasites. Principal genus Myxidium, 

 with the polar capsules at opposite poles of the spore ; M . lieberkuhni, the 

 common parasite of the pike. 



(3) CMoromyxidce, with four polar capsules ; the best known species is 

 CMoromyxum leydigi (Fig. 164), from the gall-bladder of various Elasmobranch 

 fishes. 



To the typical Myxosporidia enumerated in the above summary must be 

 added two genera recently described : 



Coccomyxa morovi (L6ger and Hesse, 765), from the gall-bladder of the 

 sardine ; the plasmodium has only two nuclei, a large and a small, and forms 

 a single spore with two valves and two parietal cells, one polar capsule, and 

 an amoebula with two nuclei. This form seems to be transitional between 

 Myxosporidia and Microsporidia, and should perhaps form the type of a third 

 suborder, the Monosporea. 



Paramyxa paradoxa (Chatton, 761), a parasite of the intestine of a pelagic 

 Annelid larva ; the multiplicative amcebula Stage is succeeded by a plasmodial 



FIG. 169. Spore of Ceratomyxa sphcerulosa. p.c., Polar capsules ; sp.p., sporo- 

 plasm ; 3., suture of the sporocyst ; x, " irregular, pale masses of undetermined 

 origin." After Thelohan, magnified 750. 



stage with two nuclei of unequal size, which multiply by fission. Finally 

 the plasmodium produces four spores, each with a single parietal cell and no 

 polar capsule. Chatton is of opinion that this species is the type of a new 

 order of Cnidosporidia, to be named Paramyxidia. 



Order II. : Actinomyxidia. The members of this group are 

 only known, up to the present, as parasites of oligochaete worms, 

 fresh-water or marine. They were discovered originally by Stole, 

 who found, in the intestinal epithelium of different species of Tubi- 

 ficidce, the spores of three genera of these parasites, named by him 

 Synactinomyxon, Hexactinomyzon, and Triactinomyxon, respectively. 

 The nature and affinities of these organisms remained for some time 

 doubtful; but the investigations of Caullery and Mesnil (769) on 

 Sphceractmomyxon stolci, a species found by them in the coelome of 

 several species of Tubificidce, established indisputably the position 

 of these parasites amongst the Cnidosporidia. Their distinctive 

 features are first, that the plasmodial stage is represented only by 

 a binucleate amoebula, which is the spore-forming phase ; secondly, 

 that the spore is of very large size and exhibits a ternary symmetry, 

 with three valves and three polar capsules. 



