INTRODUCTION. 27 



and cells of plants precludes the possibility of our consider- 

 ing them as the latter, while the appearance of a vitelline 

 nucleus, transparent but molecular fluid, a chorion or shell, 

 determines them as animal ova. It was shown to be impos- 

 sible that these eggs had been deposited in the empty shell 

 by other infusoria, or that they were the produce of some 

 entozoon. 



" 4th. That while it was impossible to determine whether 

 the vague motions of Closterium were voluntary or not, yet 

 the idea the author had formed of a suctorial apparatus, forbad 

 his classing them with plants." 



I confess I am unable to refer to any example in other 

 Alg2e of terminal globules like those present in the Closteria, 

 but neither can one be found amongst animals ; and if in 

 some respects they have an analogy with organs belonging to 

 the latter, in others they agree better with vegetable life. 

 The contained granules seem to me to differ in no respect, 

 except in position and uninterrupted motion, from other 

 granules in the same frond, and, as I have already stated, I 

 once saw the motion continue after their escape from the cell 

 precisely as in other zoospores. Meyen observes that " the 

 functions of these bodies is very difficult to determine, but 

 they are to be foand in very many Confervse, and are perhaps 

 to be likened to the spermatic animalcules of plants." 



The contraction of the internal membrane of the Closteria, 

 or the expulsion of their contents on the application of iodine 

 or other reagents, cannot be relied upon as a satisfactory test 

 for determining their nature, for the blandest fluids will, in 

 some cases, occasion violent action. If fresh water touches 

 Griffithsia setacea, the joints burst and spirt out their con- 

 tents ; and if it be applied to a species of Elachistea, the 

 granular contents are instantly thrown into commotion. In 

 certain conditions of the Closteria themselves, water will 

 produce effects like those attributed to reagents. I have 

 frequently witnessed that by the addition of water to speci- 

 mens of Closteria, which had for some time been kept merely 

 in a damp state, the frond has been ruptured, and the endo- 



