1 82 THE SPOROZOA 



gigantea, for example (Fig. 1). He attributes the forward pro- 

 gression to transverse movements of the body-surface, produced by 

 the myocy te layer, and manifesting themselves " as a shifting of 

 the cuticular striations in a direction at right angles to the long 

 axis of the animal." A muscular impulse of this kind, starting 

 anteriorly, passes along the body towards the hinder end, and 

 causes differences in the contact of the body with surrounding 

 objects. The wave of disturbance travelling along the surface of 

 the body brings about a movement of the Gregarine in a direction 

 opposite to that in which the impulse travels, and tends also to 

 cause a swinging movement of the body from side to side, which, 

 according to Crawley, can be observed very frequently in the 

 forward progression, especially when the Gregarine encounters an 

 obstacle in its path. Crawley thus refers the forward movement 

 to the contractility of the myocyte, and points out that "in 

 general, throughout the Sporozoa, the possession of muscle -fibres 

 and the power of moving from place to place go hand in hand, while 

 the forms which are not known to move lack muscular elements." 



The endoplasm, the nutritive layer of the body, is of a more 

 fluid nature than the ectoplasm, but does not exhibit any of the 

 flowing movements often seen in other Protozoa. It is always 

 crammed with great numbers of granular enclosures, representing 

 reserve nutriment stored up for the reproductive period of the 

 life-history. It is rare for the endoplasm to be vacuolated. The 

 granules increase in number as the animal grows, and render the 

 adult trophozoites very opaque, especially when they attain to a 

 large size. The most abundant and largest kind of granules are 

 the paraglycogen spherules, always present and sometimes attain- 

 ing a diameter of 10 /*. They consist of a substance allied to 

 starch and glycogen, and are characterised by the following 

 reactions : Iodine tinges them brown, changing into violet on 

 addition of dilute sulphuric acid ; they are not dissolved by pure 

 acetic acid, weak mineral acids, alcohol, or ether ; but they are 

 soluble in dilute solution of potassium carbonate and in con- 

 centrated mineral acids. Other sorts of granules may be found in 

 various Gregarines, but do not occur universally in all species. 

 Such are the so-called carminophilous granules, of irregular form, 

 and composed apparently of an albuminoid substance which is 

 stained red by picrocarmine and acetocarmine, yellow by iodine ; 

 "pyxinin" granules, characteristic of the genus Pyxinia; fat-globules; 

 and occasionally protein crystals and other more or less enigmatic 

 enclosures. 



The nucleus is always single, with the apparent exceptions due 

 to precocious association already mentioned (Fig. 23). It has the 

 form of a large spherical vesicle surrounded by a very distinct 

 membrane, and appears in life as a clear space in the opaque, 



