1 66 THE PROTOZOA 



The disease was checked only by careful examination of the food of 

 the caterpillar, and by microscopic examination of all eggs and rejec- 

 tion of the infected ones. 



No remedy is known for the many other diseases due to Sporozoa, 

 especially among domestic animals, or fresh-water fish, and careful 

 prophylactic measures analogous to those employed in stopping the 

 silkworm epidemic may be the only means of checking them. Such 

 measures have already been successfully applied to prevent the spread 

 of malaria, and the experiments which are now going on in all parts 

 of the world justify the hope that this disease will be ultimately 

 stamped out. 



F. INTER-RELATIONSHIPS OF THE SPOROZOA 



The Sporozoa, modified beyond doubt by adaptation to a parasitic 

 mode of life, have ever been a puzzle to systematists. Kolliker ('48) 

 early suggested that they are single cells, and included them in his 

 Protozoa. Stein ('48) agreed with him as to their primitive structure, 

 but was loath to regard them as single animal cells, and compromised 

 by calling them Symphyta, a group of the Protozoa. Another view, 

 developed by Henle ('45) and Bruch ('50) and taken up by Ley dig 

 ('51) and Leuckart ('52), was based upon the superficial resemblance 

 of the Gregarinida to Nematode worms. It found little support, how- 

 ever, against Kolliker's view. Still another theory of the origin of 

 the Sporozoa has been held by those who, following Gabriel ('75, 

 '80), regard these forms as plants, placing them with the Mycetozoa, 

 among the Fungi. Biitschli at first 1 favored the view that the 

 Sporozoa are derived from the Rhizopoda, basing his belief upon the 

 method of reproduction, general morphology, and physiology. Later, 

 however, 2 he considered their relationship to the Flagellidia as much 

 more close, not to the simplest forms, but to the higher types with a 

 well-differentiated cuticle. The flagellum and mouth parts, he as- 

 sumed, became lost with gradual adaptation to . the intra-cellular 

 mode of life, while the methods of reproduction became specialized in 

 response to the requirements of a new environment. This view is 

 strengthened by the close agreement in finer structures of the Grega- 

 rinida and the Flagellidia, especially as regards the differentiations 

 of the cuticle and the presence of muscular elements. Their move- 

 ments, too, recall those of the Flagellidia, especially certain species 

 of Astasia, where, in the non-flagellated condition, the plasm moves 

 forward by a peculiar peristalsis, while the secretion of a jelly from 

 the sub-cuticular or cortical plasm is identical in the two groups. The 

 nuclei show perhaps a closer resemblance to those of the Rhizopoda 



i ('83), p. 479. * ('84), p. 807. 



