Effects of Desiccation on the Rotifer 229 



clearly himself and merely states in support of this view that several 

 of his correspondents after reviving dried rotifers observed a quan- 

 of sticky material adhering to them. This is not surprising since 

 the cement glands at the tip of the foot are continually secreting 

 a sticky substance by means of v^hich the animal fastens itself 

 to soHd objects and which under certain conditions may be poured 

 out in considerable quantities. The mere presence of a small 

 amount of this substance seems like rather slender evidence on 

 which to base such far-reaching conclusions. 



Hudson ('89) is more definite in his statements. In describing 

 the appearance of a group of rotifers dried on a piece of paper he 

 says, " Each Philodine is the center of a patch of glutinous secre- 

 tion which meets the similar patches surrounding its neighbors 

 in a succession of straight lines; so that the whole group has quite 

 a tesselated appearance. Here and there where fibers pass 

 over or through a group long tongues of the secretion stretch 

 from the animals to the fibers." The apperance observed by 

 Hudson is a very common oneingroupsof dried rotifers; the inter- 

 pretation he makes of it, however, is entirely wrong. What he 

 thought to be the "glutinous secretion" is nothing but the cuticle 

 of the animal from which the internal organs have shrunken more 

 or less in the process of drying and which so closely resembles a 

 secretion of some sort as to be easily mistaken for it on superficial 

 observation. In the present experiments many careful observa- 

 tions were made on rotifers during the processes of drying and 

 subsequent revival with the result that absolutely no evidence could 

 be obtained that any such substance is secreted at the time of dry- 

 ing or dissolved when water is added. By adding a little methyl- 

 ene blue to the water before the rotifers dry, it is easy to follow 

 the process in detail. This stain colors no part of the living animal 

 but that portion of the cuticle which is outermost when it is con- 

 tracted. If the animals are not allowed to remain in it too long 

 there are no injurious effects and normal recovery occurs. Roti- 

 fers thus stained and then placed in clean water before being dried 

 show very clearly all of the changes that occur during the process. 

 If any secretion were poured out in the manner described by Davis 

 and Hudson it should be visible outside of the stained cuticle. 



