38 M. J. de Guerne on the 



There is, however, nothing astonishing in finding distri- 

 buted over the whole surface of the globe animals which are 

 easily diffused, and which, on the one hand, either on moun- 

 tains or in high latitudes, support a very intense cold, and, on 

 the other, live in water at a high temperature, as especially in 

 Egypt. 



It is probable that future investigations will lead to the 

 discovery in very different localities of the new species above 

 described, as well as oi A. Ebheshornei, at present noted only 

 at a single point in England. The example of A. helvetica 

 (described in 1883) suffices to show with what rapidity data 

 may be brought together upon the geographical distribution 

 of an animal when special researches lead to its being collected 

 by suitable processes. 



On the Genus Ascomorpha. — Before concluding this chapter 

 I will say a few words on the Ascomorphce, which are usually 

 classed, although wrongly, in the family Asplanchnidje. 

 The very small Rotifera which belong to this genus are very 

 difficult to study, and still appear not to be satisfactorily 

 known. The absence of an anal aperture, which has led to 

 their being approximated to Asplanchna, is not a character of 

 prime importance, for it almost certainly results from an 

 adaptation to a particular mode of life. To unite the forms 

 which present this peculiarity without taking into account 

 other details of structure is to fall into an error like that 

 which would consist, for example, in establishing a family for 

 all the Ilotifera which are destitute of a foot. 



However imperfectly investigated, it is evident that the 

 feeble mastax of the Ascomorphce in no degree resembles the 

 powerful maxillffi of Asplanchna. The same observation 

 applies to the stomach, the singular diverticula of which have 

 been noticed by Gosse and Bartsch in two different species. 

 The latter zoologist, to whom, indeed, we are indebted for the 

 fullest information upon these animals, has described, in 

 Ascomorpha saltans, a sort of resistant envelope bearing pro- 

 jecting and symmetrical ridges. Seen from the dorsal surface, 

 with its four ridges converging towards the bottom, this 

 envelope presents some analogy, always excepting the denti- 

 culation of the aperture, with the test of certain species of 

 Anurcea {A. striata, Ehr., among others). Lastly, the Hun- 

 garian author indicates in the same type the existence of a 

 sort of stout tentacle, quite unknown in the Asplanchna. I 

 have thought it desirable to reproduce here (tig. 5) the figure 



