24 



PROTOZOA 



The Sporozoa are divided into four sub-classes, differing from one 

 another according to the form and development attained by the 

 euglena phase. We shall place the most highly developed first, not 

 only because our knowledge about it is most complete, but because 

 it is possible that one at least of the other sub-classes is derived by 

 degeneration from it. 



SUB-CLASS I. Gregarinidea, Butschli (9). 



Characters. Sporozoa in which the euglena phase is dominant, 

 being relatively of large size, elongate in form, definitely shaped, 

 having contractile but not viscid cortex, and exhibiting often active 

 nutritional and locomotor phenomena. Though usually if not 

 invariably cell-parasites in early youth, they become free before 

 attaining adult growth, and inhabit either the body-cavity or the 

 intestine of their hosts. Many spores are produced in the encysted 

 phase. The spores have an oblong, sometimes caudate coat, and 

 produce each one or several falciform young. At present only 

 known as parasites of Invertebrata. 



Flo. XVII. Sporozoa. i, 2. Monocystis ayMs, Stem ; x 250 ; from the testis 

 of the Earthworm. Two phases of movement a ring-like contraction 

 passing along the body from one end to the other. 3. Individual of the 



same species which has penetrated in the young stage a sperm-cell of the 

 Earthworm, and is now clothed as it were with spermatoblasts. 4. 



Monocystis magna, A. Schmidt, from the testis of the Earthworm (L. terres- 



trig, L.). Two individuals, which are implanted by one extremity at 6 in 

 two epithelial cells of the rosette of the spermatic duct, a, nucleus of the 

 Monocystis. 5. Tailed chlamydospores of Monocystis sxnuridis, 



Koll. 6. Two M. agilis encysted, spores forming on the surface of the 



protoplasm. 7. A similar cyst f urtheradvanced in spore-formation (see 



Fig. XVIII.). 8. Spore of M. agilis, now elongated but still naked. 

 a, nucleus. X 1400. 9. The spore has now encased itself in a navicula- 



shaped coat, a, nucleus. 10. The spore protoplasm has now divided 



into several falciform swarm-spores, leaving a portion of the protoplasm 

 unused, b, Schneider's residual core. 11. Optical transverse section of 

 a completed spore, b, Schneider's residual core. 12. Chlamydospore 



of Klossia chitonis, nov. sp., from the liver of Chiton (original.) 13, 



14. Chlamydospore of Monocystis nemertis, Koll., liberating falciform 

 young, b, Schneider's residue. 15. Monocystis pellucida, Koll. (from 



Nereis) ; x 150 ; to show the very thick cortical substance and its fibrilla- 

 tion (after Lankester, 54). 16. Monocystis ssenuridis, Koll., two indivi- 

 duals adhering to one another (a syzygium). For spores see 5. 17. Mono- 

 cystii aphroditx, Lankester (55) ; x 60 ; remarkable among Monocystids 

 for its long proboscis resembling the epimerite of some Septata. 18. 



Klossia helicina, Aim. Sclm., from the kidney of Helix hortensis. A. single 

 cell of the renal epithelium in which a full-grown Klossia is embedded. 

 a, nucleus of the Klossia ; a', nncleus of the renal cell. 19. Cyst of 



Klossia helicina, the contents broken up into spherical chlamydo- 

 spores. 20. Single spore from the last, showing falciform young and a 

 Schneider's residue i. 21. The contents of the same spore. 22. A small 

 renal cell of Helix containing two of the youngest stage of Klossia. 23. 

 Monocystis saf/ittata, Leuck., from the intestine of Capitella capitata', 

 x 100. 24 to 31. Coccidium ovtforme, Leuck., from the liver of the Rabbit: 

 24, adult individual encysted ; 25, the protoplasm contracted a, 

 nucleus ; 26, 27, division into four spores, as yet naked ; 28, 29, the spores 

 have acquired acovering, i.e., are chlamydospores, and each contains a single 

 falciform young ; 30, 31, two views of a Chlamydospore more highly magni- 

 fied so as to show the single falciform young (from Leuckart). 32. Klossia 

 octopiana, Aim. Schn., from Cephalopoda, a, nucleus; b, cyst-membrane, 

 x 200 diam. 33. Single spherical spore of the same ; x 1400 diam ; 

 showing numerous falciform young, and b, Schneider's residue. 34. 

 Myxidium Lieberkutmii, BUtschli, one of the Myxosporidia, from the 

 bladder of the Pike (Esox); creeping euglena phase, showing strongly 

 lobed amoeboid character (pseudopodia and undifferentiated (?) cortex) ; 

 X 60 diam. 35-39. Eimeria falcijormis, Eimer sp., from the Mouse : 

 35, an adult non-encysted individual inhabiting an epithelial cell of the 

 intestine of the mouse ; 36, encysted phase ; 37, clear corpuscles appear 

 in the encysted protoplasm ; 38, the protoplasm now forms a single 

 spore containing several falciform young ; 6, Schneider's residue ; 39, 

 isolated spore showing falciform young, and b, Schneider's residue. 

 40. Chlamydospore of Myxobolus Mulleri, Butschli, one of the Myxo- 

 sporidia from the gills of Cyprinoid Fishes, a, nucleus ; b, refringent 

 corpuscle ; c, polar body or thread-capsule. 41. A similar Chlamydo- 

 spore which has ejected the filaments from its thread capsules. 42. 

 Chlamydospore of a Myxosporidium infesting the kidney of Lota wtlgaris. 

 c, polar body (psorosperm of authors). 43, 44. Chlamydospores of 

 a Myxosporidium from the gills of Perca (psorosperm of authors). 

 Compare with the tailed Chlamydospore of Monocystis sxnuridis, 5. 45 

 -47. Drepanidiutn ranarum, Lankester, the falciform young of an 

 unascertained Coccidiide infesting the Frog (supposed by Gaule to be pro- 

 duced by the blood corpuscles) : 45, specimen stained by iodine ; 46, red- 

 blood corpuscle of Frog, showing b, two contained Drepanidia, and a, the 

 nucleus of the blood corpuscle ; 47, living Drepanidium. 48. Chlamy- 

 dospore of Lieberkiihn's Coccidium of the Frog's kidney, perhaps belong- 

 ing to the life-cycle of Drepanidium ranarum. The spore contains 

 two falciform young (Drepanidia?) and a Schneider's residue. 49. 

 Chlamydospore of Monocystis thalassemie, Lankester, containing nume- 

 rous falciform young. 50, 51. Sarcocystis Miescheri, Lankester: 50, 

 falciform young escaped from chlamydospores ; 61, adult euglena phase 

 inhabiting a striated muscle fibre of the Pig. 



ORDER 1. HAPLOCYTA, Lankester. 



Characters. Gregarinidea in which there is never at any time a 

 partition of the medullary substance into two or more chambers. 

 The euglenoid is always a single contractile sac with, one mass of 

 medullary substance in w r hich Heats the large vesicular transparent 

 nucleus. Spores larger than in the next group, each producing 

 several falciform young. 



Genus unicum. Monocyslis, Stein, 1848. The various generic 

 subdivisions proposed by Aim. Schneider (48), and accepted by 

 Butschli, appear to the present writer to have insufficient characters, 

 and serve to complicate rather than to organize our knowledge of 

 the subject. We do not yet know enough of the sporulation and 

 subsequent development of the various monocystic Gregarinides to 

 justify the erection of distinct genera. 



Monocystis agilis, Stein, Fig. XVII. 1, 2, 3, 6, 7, 8, 9, 10, 11, 

 and Fig. XVIII. is the type. The other species of Monocystis 

 occur chiefly (and very commonly) in marine Annelids, Platyhel- 

 minthes, Gephyrsea, and Tunicata ; not in Arthropoda, Mollusca, 

 nor Vertebrata. The only definite differences which they present 

 of possibly more than specific worth, as compared with M. agilis, 

 are in the form of the chlamydospores, which are sometimes tailed, 

 as in M. s&nuridis (Fig. XVII. 5), and in M. nemertis (Fig. XVII. 

 13) and M. sipunculi, and further also certain differences in the 



fneral form, as for instance the anchor-like M. sagittata (Fig. 

 VII. 23), and the proboscidifcrous M. aphroditie (Fig. XVII. 17). 

 The fine parallel striation of the cuticule in some species (M. 

 scrpulse, &c.) might also be made the basis of a generic or sub- 

 generic group. 



On the whole it seems best to leave all the species for the present 

 in the one genus Monocystis, pending further knowledge. It seems 

 probable that more than one species (at least two, M. agilis and M. 

 magna] infest the common Earthworm. 



ORDER 2. SEPTATA, Lankester. 



Characters. Gregarinidea in which in the adult the medullary 

 substance is separated into two chambers a smaller anterior (the 



