MICROHYDRA RYDERT. 631 



The otliei* mode of reproduction or of propagation is by- 

 branching. This was seen in two instances, one of them 

 from the same polyp that had been already known to have 

 produced four larvae, and the branch originated upon the 

 same side and locality. The action was even more rapid in 

 that the branch appeared and completed its capitulum within 

 twenty-four hours. Its formation was not preceded by the 

 turgidity and granular appearance mentioned in the case of 

 the larval buds, but an uninterrupted sequence of clear endo- 

 dermal cells was traced from the main stem into the branches. 

 These branches were, possibly, later constricted off, as in the 

 case of the common Hydra, to form independent hydroids, 

 but I did not see it. 



During the twelve years intervening between 1885 and 

 1897 collections had frequently been made from the 

 Schuylkill canal, on the banks o£ the Schuylkill River, far 

 above tide water, and from a water-shed quite separate from 

 that supplying the locality previously mentioned. The 

 special objects of search were here also stones bearing 

 localised forms of Bryozoa, and, as before, I found M. 

 ryderi amongst them. These stones were dredged up from a 

 depth of six or seven feet at a place where a continuous 

 rush of water kept them from being covered, and their 

 encrusting fauna from being smothered by the mud that in 

 other places embeds the canal. 



Whether, under these circumstances, medusae are commonly 

 and normally developed, and their eggs hatch into hydroid 

 polyps, or whether nature here provides more abundantly the 

 asexual larval method of reproduction above described must, 

 for the present, remain a problem. 



In concluding, it is hardly necessary to invite the attention 

 of scientists to the fact that we have, in these three fresh- 

 water forms, an equal number of species, no one of which has 

 been conclusively studied ; that their appearance in three of 

 the five grand divisions of the earth points very plainly to 

 the probability that closer methods of research may very soon 

 discover others in familiar but unsuspected places ; that, 



