Statohlasts of Fresh-water Polyzoa. By C. F. Rousselet. 145 



and to find out exactly what happened. To take a particular case, there 

 were two forms, which had heen j-eferred to distinct genera, PlumaieMa 

 and Alcyonplla. Phmiatella grew in a diffuse way, with large spaces 

 between the branches, and it could frequently be found under the leaves 

 of water-lilies. AlcyoneUa formed large compact masses on the object 

 on which it was growing, and its tubes were closely packed, standing 

 vertically to the surface and in close lateral contact. It had been said 

 that if cut in half old colonies presented a structure similar to that of 

 an onion, due to the presence of several annual rings ; and that this was 

 due to the fact that at the end of the season the soft parts disintegrated, 

 leaving the tubes, which contained a numbei- of statoblasts. In the 

 following spring the statoblasts which were left in the old tubes germin- 

 ated, the junction of the new growth and of the old tubes forming an 

 annual ring. 



It has been considered that Plumatella and AlcyoneUa are different 

 forms of one and the same species ; that if one statoblast germinates on 

 a leaf it grows out into the diffuse pattern which generally occurs in 

 Plumatella ; while, if a number of statoblasts are deposited close together 

 in one place, the new colonies produced by their simultaneous germina- 

 tion have not sufficient room and the tubes are crowded, thus giving 

 rise to an AlcyoneUa colony. The doubt that exists in this case (and in 

 others) might be resolved by experimental work. 



He would like to call attention to a point of some practical importance, 

 namely, that there might be danger in throwing away in a sink living 

 ■statoblasts. There were cases on record in which Polyzoa had made 

 their way into pipes for the supply of water, where they had flourished 

 in an extraordinary way, causing all kinds of difficulties which it was 

 extremely difficult to get over. The Polyzoa are animals which can 

 grow well in pipes containing unfiltered water in which there are 

 diatoms. In Hamburg and other places they have given rise to serious 

 trouble in the pipes supplying the houses with water. He did not 

 suppose there was much danger of introducing them into the pipes of 

 waste-systems, but as there was a possibility of infecting surface-water 

 systems, it would be well to exercise care on this point. 



Mr. Earland said that no one could look at such a collection of 

 statoblasts without recognizing that some, at any rate, bore a strong 

 superficial resemblance to the mysterious bodies known as Xanthidia, 

 which were found in flints. Was it anything more than similarity of 

 form ? Years ago he had been interested in Xanthidia and made a 

 collection of them. He came to the conclusion that they had originally 

 been of a horny nature because many specimens were ruptured and 

 showed ragged edges at the fracture. Did Dr. Harmer think there was 

 any connexion between the objects other than the similarity of form, 

 which was especially noticeable in Gristatella and PectinateUa ? Of 

 course, the fact that the chalk flints were of marine origin was a strong 

 argument against any such connexion, but, on the other hand, he had 

 himself found fresh-water statoblasts in marine shore-gatherings from 

 the Clare Island area, and the bodies in chalk flints might conceivably 

 have been derived from a cretaceous fresh-water polyzoou. 



Mr. D. J. Scourfield expressed his gratitude to Mr. Rousselet for 

 bringing before the Society such a fine collection of statoblasts, 



