110 



remains always almost the same. Diving downwards 

 and upwards , they move in circular lines, as mole- 

 cules do. In the Closterium Lunula , several are 

 often found 5 in the Closterium costatum^ never more 

 than one 5 in the Closterium didymotocum we see 

 two twin globules (fig. 65. e.) , forming only one 

 body, the union of which is still visible. 



In a series of species of this genus, I have seen 

 globules without apparent bladder, moving freely 

 towards the empty point of the valvules: which 

 motion is distinctly seen in the Closterium acumina- 

 tum (fig. 59. e.). The vesicle surrounds the coat 

 contiguous to the cuirass , and that coat cannot be 

 separated from it but by galvanic strokes. 



When the Closteria die, these animalcules retreat 

 downwards, and present nothing more than a scar- 

 cely visible spot. In squeezing them under a flat 

 and very thin bit of glass, I sometimes succeeded in 

 obtaining them single, and then they appeared to me 

 quite spherical , without the least mark of adhesion. 



In the Closterium Lunula and didymotocum, we 

 discover under the rotatory bladder, and above the 

 first, the marks of an intestinal tube in right line 

 (e. e.), surrounded with the green substance, which 

 fills the animalcules. In spite of the finest instru- 

 ments and innumerable trials, I never succeeded in 

 separating this tube, because the green substance, 

 half liquid , mixed with large oily drops , cover the 

 whole , and baffles every direct observation. 



Speaking of the intestines , we must mention the 



