144 THE PROTOZOA 



ently take the place of the paraglycogen granules, although of similar 

 chemical nature, but slightly different in their reactions. The latter 

 are also rather questionable inclusions in certain DidymopJiyes. In 

 the Coccidiida all adult forms are characterized by the presence of 

 so-called plastic grannies. These are globular, strongly refractive 

 granules of slightly variable size which react differently from the 

 glycogen granules, remaining unchanged in sulphuric acid and stain- 

 ing yellow with iodine. Here also are found the so-called cJiromatoid 

 granules, which are distinguished by their affinity for haematoxylin, and 

 are probably albuminoid in nature. In the Haemosporidiida or blood- 

 infesting Sporozoa, the effect of the intra-corpuscular life is shown 

 by the presence of pigmented granules (melanin) of black, yellow 

 ochre, or red color resulting from the disintegration of haemoglobin. 

 In the majority of the Sporozoa the cell-body consists of a more or 

 less sharply differentiated ectoplasm and endoplasm, while even a 

 third layer, mesoplasm, is said to have been observed in some forms 

 (Cohn, '96). It is possible that these different zones are function- 

 ally specialized, a supposition first made by Labbe ('96) in connection 

 with the Coccidiida, and repeated by Doflein ('98) in connection with 

 the Myxosporidiida. As in the Sarcodina and Mastigophora, the 

 ectoplasm may be plastic, yielding to the pressure from within and 

 thus giving rise to pseudopodia (Monocystis ascidia, Siedlecki, '99, 

 Myxosporidiida), or it may be modified into a hard and tough cuticle, 

 which offers a good protection for the cell-body within. Again, it 

 may be modified into a complex membrane, plastic and capable of 

 various kinds of motion and similar to that of the higher types of 

 Flagellidia. The most highly differentiated ectoplasm is found in the 

 Gregarinida, where it forms a dense cortical layer about the body, 

 while its outermost part is transformed into a complex membrane. 

 In some cases the inner cortical layer of the ectoplasm is carried 

 across the cell, forming a partition dividing the organism into two 

 portions which are known as the protomerite and the deutomerite, 

 the nucleus being in the latter. The non-nucleated portion is often 

 further differentiated into an apparatus called the epimerite, which usu- 

 ally develops hooks or anchors used for attaching the animal to its 

 cell-host. The organism thus appears to be multi-chambered, and the 

 presence or absence of such chambers was formerly regarded as a 

 good basis for classification ; but it has been shown, especially by 

 Leger ('92), that the partitions vary considerably in the same species, 

 and even in the same individual, at different times, and in the recent 

 systems of classification this feature has been discarded in determining 

 the limits of the larger divisions. The epimerite, which is so important 

 in holding the lumen-dwelling parasites in place, may be simple or 

 branched ; plain, like a knob or a rod ; branched with filiform, or flat 



