8 THE ZOOLOGIST. 



animal, an elliptical, thick-skinned, yellow body (fig. 4), which I 

 call here the inner cyst. 



This inner cyst is smooth, and has no trace of limbs. It is 

 considerably less in size than the outer cyst, in which it lies 

 loosely. Just after it is formed it contains a complete animal, 

 possessed of all the normal organs. This may be squeezed out, 

 and may be seen to move feebly. 



When a large number of cysts were broken up, after the lapse 

 of abouT; a week from their first observation, it was found that a 

 large proportion of the inner cysts had undergone further change. 

 The cyst no longer contained a complete animal. Most of the con- 

 spicuous organs had disappeared — claws, pharynx, teeth, &c. — 

 and the animal would not have been recognized as a Tardigrade 

 had its antecedents not been known. Only the pigment-spots, 

 commonly called eyes, and the fat-cells in the blood were recog- 

 nizable. There was a faint segmentation within the cyst, three 

 transverse furrows dividing the body into four nearly equal parts. 

 The pigment-spots were very diffuse. 



The animal contained in the inner cyst is so unlike a Tardi- 

 grade that I have entertained the idea that it might be some 

 parasite — possibly a Turbellarian or other worm. The com- 

 plexity of the series of changes by which the final cyst is pro- 

 duced, the constant form and size of the outer cyst, and the 

 presence of all the organs till the last stage is reached — all tell 

 against the theory of parasitism, and lead to the conclusion that 

 we have to do with a normal process in the life-history of the 

 animal. 



What may be the meaning of these remarkable changes we 

 need hardly attempt to guess till the further stages have been 

 observed. Cysts of other species have been seen, in which there 

 were active animals which I supposed were about to emerge, 

 but in view of the history of M. dispar, partly traced above, we 

 may rather suppose that these cysts had just been formed, and 

 that the process of simplification had not yet taken place. 



Till the full history is known it will remain inexplicable why 

 the double moult should take place, the animal at each moult 

 assuming a different form ; and, finally, why the individual 

 should undergo such a profound simplification. The curious 

 outer cyst may be regarded not as the result of a moult, but as 



