326 Fault.— The Cytology of 
noteworthy that, within the limits of the order, bisexual and unisexual 
species exist, and that, in connexion with the latter, heterospory and di- 
morphism have arisen, but concerning the associated cytological phenomena 
we know nothing. These and other matters provide abundant cause and 
stimulus for investigation. Since up to the present no contributions, apart 
from two brief articles by the writer (Faull, ’ 05 , ’ll), have been made on 
their cytology, several forms have been placed under investigation in the 
hope of discovering an answer to some of the problems that await solution. 
Some of the results obtained are presented here and some will be published 
in other memoirs. In this connexion, I wish to express my gratitude to 
Professor Roland Thaxter, who has most generously placed the rich stores of 
his intimate knowledge of this group at my disposal, and who has kindly 
examined some of my preparations and extended many other courtesies. 
Material and Methods. 
Laboulbenia chaetophora occurs on the edges of the elytra and the free 
tip of the abdomen of several species of the genus Gyrinus , the familiar 
‘ whirligigs ’ common on ponds and along the quieter margins of streams 
and lakes. With it is frequently associated Laboulbenia Gyrinidarum , 
though in the two rather remotely separated regions from which the material 
for the investigations described in this paper was collected, the former species 
was abundant and the latter rare in one locality, while in the other the 
conditions were reversed. 
L. chaetophora seems to prefer the free tip of the abdomen, on which 
it often grows in tufts of from two to ten or more individuals, and L . Gyrini- 
darum the margins of the elytra, which are not uncommonly fringed with 
a growth of the plants of this species. 
L . chaetophora is the larger form of the two, sometimes attaining 
a length approximating a millimetre and a width one-fifth as great, a peri- 
thecium up to 400 \x long, and a receptacle 525 /x or more. The smaller 
form rarely reaches half a millimetre in entire length and 160 /x breadth. 
There are other well-marked distinctions, all of which are noted by Thaxter 
in the second volume of his monograph. 
Of the available species of Laboulbenia , L . chaetophora presents the 
advantages of size, and mode and place of occurrence on the insect, though 
both lend themselves rather well to the manipulations about to be described. 
The material was collected in the neighbourhood of Guelph and Ottawa, 
Canada. While most of it was of the larger species, it was impracticable 
if not impossible to separate the species, and especially to distinguish the 
younger stages of the two forms from one another. However, they are 
so nearly alike and so closely allied that chances of error are practically 
negligible. 
