ROTATORIA OF THE UNITED STATES. 
71 
making of new species because the observer finds some structure not previously figured 
or described in wTiat would otherwise be considered an old species. It must be 
recognized that very few of the older figures and descriptions are in any sense 
complete; it was the purpose of many of the older authors to give merely such a 
figure and description as would lead to ready recognition of the animal, not to give an 
exhaustive anatomical account. Moreover, the improvements in optical instruments 
and in technique have been such as to enable even the amateur to see much that 
formerly remained hidden to the best investigators. 
A third opportunity for the introduction of confusion into the study of the 
Rotatoria lies in the great variability of many forms. There are few species that are 
not sufficiently variable to permit an observer to find specimens that differ from the 
type enough to allow him to immortalize his name by appending it to a synonym, if his 
ambition runs in that direction. Rousselet (’97) has already pointed out that many 
of the recent new species are but slight variations of well-known forms. It must be 
recognized, however, that the limits of variability are not easily defined, and that it is 
often very difficult to say whether a given specimen should be considered a new 
species or a variation of an old one. Mistakes from this source are therefore to a cer- 
tain extent excusable, while those resulting from the first two causes above mentioned 
are usually due to carelessness or ignorance. 
To describe a new species, one should therefore have access to all the papers in 
which new species have been described since the publication of Hudson and Gosse’s 
Monograph, or at least to all papers describing any species belonging to the genus 
under consideration. The titles of the papers bearing directly on the genus of which 
it is proposed to describe a new species may be determined — up to 1897, at least — 
from Mr. Charles Rousselet’s lists of new species of Rotifera (Rousselet ’93 and ’97). 
As a further precaution against error, it would be well to submit either mounted speci- 
mens or drawings and notes on proposed new species before publication to someone 
thoroughly competent to judge as to their claims. Mr. Charles Rousselet, 2 Pembridge 
Crescent, Bayswater, London W., England, is doubtless as well acquainted with the 
Rotifera as anyone in the world, and is always willing, with uniform courtesy and 
kindness, to give expert advice as to the publication of what seem to be new species. 
On account of the recent great multiplication of new species, a description of a 
new rotifer should be accompanied by a careful comparison with any other species of 
the same genus that at all nearly resemble it and the points of difference brought out 
clearly. In a number of recent cases the lack of ground for giving a new name would 
at once have been evident if this had been done. For example, Stenroos (’98) in his 
recent valuable paper on the animal life of Lake Rurmijarvi, in Finland, after describ- 
ing as new Cathypna magna n. sp., gives a list of the known species of Cathypna, 
among them Cathypna ungulata Gosse. A careful comparison of Cathypna magna 
Stenroos with Cathypna ungulata Gosse would have disclosed their identity. 
The publication of a new species without a figure, which has been practiced by 
some American authors, as well as by some of those of Europe, is greatly to be 
deprecated. Usually the figure is the most important part of the account of a rotifer, 
and a description could, as a rule, be much better dispensed with than a good figure. 
To sum up, therefore, anyone who proposes to publish a description of a rotifer 
as new should fulfill the following conditions: 
1. Rot only Hudson and Gosse’s Monograph, but all subsequent papers contain- 
ing descriptions of rotifers in any way related to the one in hand, should be consulted. 
