THE SPOROZOA 



281 



panied by the excretion of a granular substance which is left behind 

 as the animal moves forwards. Locomotion effected in this manner, 

 by means of a posteriorly situated propulsive pseudopodium 

 (" Stemm-pseudopodium," Doflein) is unique amongst Protozoa, and 

 possibly represents a primitive method of progression, which in 

 the non-amoeboid Telosporidia is reduced to the shooting out of a 

 secretion alone, without any extension of protoplasm, from the 

 posterior end (see p. 181). 



The pseudopodia, whatever their characters, are never used for 

 the ingestion of solid food-particles, as in Amoebae. In free forms, 

 however, they serve for fixation, as well as for movement. Besides 



. 'St pS. 



FIQ. 87. 



Leptotheca agilis, Thel., young trophozoites in which spore-formation has scarcely commenced, 

 after Doflein. a and b, two figures of the same individual drawn at intervals of rather more 

 than a minute, c, an individual moving forward (in the direction of the arrow) by means of a 

 propulsive pseudopodium (st.ps) at the hinder end ; the trail of granules left by the 

 propulsive pseudopodium should be represented much longer, ps, pseudopodia ; st.ps, 

 propulsive pseudopodium ; p.sp, pansporoblast. 



amoeboid changes of form, the trophozoite may exhibit contractile 

 movements like those of Gregarines, resulting in ring- like con- 

 strictions or flexions of the body. 



In many cases, especially amongst encysted forms, the ectoplasm 

 has its protective function developed at the expense of its motility, 

 and becomes converted into a firm envelope, which may be finely 

 fibrillar, as in Glugea anomala, or vertically striated, as in Myxidium 

 lieberkuhnii (Fig. 88). In the last-named species the character 

 of the ectoplasm is variable, and in other cases it may give rise to 

 lobose pseudopodia, or be covered with a sort of fur of fine 

 non-motile filaments. These differentiations of the ectoplasm are 

 important for comparison with the envelopes of the Sarcosporidia. 



The endoplasm has a distinctly alveolar structure, and is some- 



