1 68 THE SPOROZOA 



Delage and He"rouard [2] in their classification made use of the char- 

 acter of the sporozoite or protoplasmic germ within the spore, and divided 

 the class into (1) Rhabdogeniae, " with sporozoite of definite form, generally 

 falciform (arqude) " (Gregarinida, Coccidiidea, Haemosporidia, and Sarco- 

 sporidia) ; and (2) Amoebogeniae, " with amoeboid sporozoite " (Myxo- 

 sporidia). This classification has the disadvantage, however, of separating 

 the two nearly allied groups Myxosporidia and Sarcosporidia, and it has 

 not been followed by any subsequent writers. 



Mesnil [6], making use of names invented by Metschnikoff, divides 

 the Sporozoa into Ectospora (Gregarinida, Coccidiidea, and Haemosporidia) 

 and Endospora (Myxosporidia, Sarcosporidia, and Haplosporidia). In the 

 Ectospora, the sporulation takes place at the close of the trophic period, 

 and the spore-mother-cells (sporoblasts) are formed at the periphery of 

 the sporont ; in the Endospora, spore-formation goes on during the growth 

 of the trophozoite, and the spore-mother-cells (pansporoblasts) are cut off 

 in the interior of the body (p. 283). 



In the sequel the classification of Schaudinn into two groups, Telo- 

 sporidia and Neosporidia, as defined above (p. 166), is followed. It is seen 

 that, as compared with the classifications of Labbe" and Mesnil, the dis- 

 tinction depends rather on the mode of defining the two subdivisions 

 than on essential differences in the plan of grouping the orders. 



SYSTEMATIC REVIEW OF THE SPOROZOA 

 SUB-CLASS TELOSPORIDIA. 



Sporozoa in which the reproductive phase of the life-cycle is distinct from, 

 and follows after, the trophic phase. 



ORDER 1. Gregarinida. 



The Gregarinida, commonly known as Gregarines, are an order 

 of the Sporozoa remarkable for the degree to which structural 

 complexity of the individual, and adaptive specialisation of the 

 species, are carried. On the other hand, the life-cycle is usually 

 extremely simple. It might, in fact, be said, speaking generally, 

 that the Gregarines are the highest of the Sporozoa from the 

 standpoint of morphology, and the most differentiated from the 

 point of view of taxonomy, but are at the same tinle amongst the 

 simplest as regards reproductive phenomena. Their distinctive 

 characters are as follows : The trophozoite commences its growth 

 typically as an intracellular parasite, usually, if not always, of an 

 epithelial cell ; never of a blood-corpuscle. It soon outgrows the 

 host-cell, and bulges from it, and finally drops out into an internal 

 cavity of the host, usually the digestive tract, but often the 



