162 JULIAN S. HUXLEY. 



outside walls continue the lines of the body : the whole is 

 marked off by a circular groove, thus rather resembling the 

 sucker of an Octopus. 



Leaving the details of these organellae for the present, I 

 will now describe the main body of Ganymedes. This is of 

 the usual type seen in motile Gregarines. It is covered with 

 a firm cuticle, the longitudinal striations on which can be 

 easily seen (figs. 6, 10, 11). Just beneath this appears in 

 many cases a pale ectoplasmic layer, lacking the granules 

 of the central endoplasm : and though I have never been able 

 to demonstrate actual myonemes, yet from what we know of 

 other Gregarines it is probable that this layer is the seat of 

 the contractile structures which this free-swimming creature 

 must possess. The endoplasm proper is denser, and con- 

 tains granules. The whole cytoplasm is of reticular or 

 alveolar structure. 



The nucleus lies more or less iu the centre of the body: 

 it is ellipsoidal : the folds and processes sometimes seen at 

 one end of it (fig. 15) being probably artefacts. Its breadth 

 is often very nearly that of the Gregarine, and it would some- 

 times touch the cuticle except that when it is large the body 

 bulges out slightly round it. It possesses a thin but distinct 

 nuclear membrane, within which is a reticulum with granules 

 on the threads — sometimes loose with largish grains (fig. 14), 

 sometimes finer (fig. 15). In addition there is present a 

 deeply staining spherical nucleolus, usually towards the cup 

 end of the nucleus. In it, a thin outer rind usually stains 

 deeper than the centi-al medulla, which is filled with clear 

 vacuoles of various sizes (figs. 14, 15). With Mann's 

 methyl-blue-eosiu it stains usually bright crimson to claret- 

 colour, often with a violet crescentic area on one side. 



Returning now to the anterior extremity, we find that in 

 some cases there is, as above stated, a distinct stalked sphere 

 (figs. 7 — 10). This is covered with a cuticle thinner and less 

 firm than that of the body, the two passing into each other 

 round the narrowest part of the neck (fig. 7). The sphere is 

 filled with a quite homogeneous fluid, except at the extreme 



