230 Transactions of the Society. 



about South American Eotifera, with tables showing the distribution 

 over the continent. 



Whenever possible, the animals were studied on the spot and 

 in the living state. Subsequent study of the moss-dwelling species, 

 was rendered possible by the usual method of drying the moss and 

 afterwards reviving the animals. The pond-dwellers were usually 

 narcotized and fixed by Kousselet's method. As the narcotic and 

 osmic acid were used by guess, and without examination during 

 the process, it is not surprising that only a small proportion of the 

 animals were fully extended. While this is a disadvantage in the 

 case of the soft-bodied species, and accounts for their paucity in 

 the lists (apart from the Bdelloids), it is a distinct advantage in 

 working with the loricate kinds. 



The number of known species of Eotifera has greatly increased 

 since Hudson and Gosse put out their great Monograph {11), as 

 Mr. Rousselet's four lists of new species indicate. Mr. Kousselet's 

 work in this direction is invaluable. Without it the student would 

 enter a wilderness indeed, when he took up the study of the 

 Rotifera. The Monograph itself was a pioneer work, and additions 

 of species discovered while it was in the press were so many that 

 the supplement is disproportionate to the main work. A new 

 revision would be highly desirable, were it only to arrange all H. 

 and G.'s species in natural order. A better understanding of many 

 species nowadays, and the addition of hosts of new species, renders 

 a new Monograph a crying need. 



Some species occur several times over in H. and G. under 

 different names, species which they rejected have been established, 

 and others which they accepted must be discredited. A revised 

 Hudson and Gosse would be such a colossal task that it is not to 

 be wondered at if those qualified to undertake it shrink from 

 doing so. 



Mr. Rousselet has long advocated meeting the difficulty in a 

 measure by a series of monographs of families, or even of genera. 

 Thus we have his own " Synchaeta," Jennings's " Rattulidse," 

 Hlava's " Melicertidge," Dixon-Nuttall and Freeman's " Diaschiza." 



EXPLANATION OF PLATE IX.— continued. 



Fig. 5a. — Philodina americana sp. n. Fully extended, creeping. 



,, 5b. Ditto. Jaws. 



,, 5 c. Ditto. Foot. 



,, 5d. Ditto. Optical section of neck. 



,, 6a. — Habrotrocha. unnamed species. Dorsal view, 



,, 66. Ditto. Ditto. Lateral view. 



„ 6 c. Ditto. Ditto. Foot. 



,, 6d. Ditto. Ditto. Corona in retraction. 



„ 1. — Pleuretra brycei, variety. 



,, 8. Ditto. Another variety. 



,, 9. — Notops brachion^is y&v . spinosus. 



