A ROTIFER PARASITIC IN THE EGG OF THE WATER-SNAIL. 483 



When in the compressor, without narcotic, the little Eotifer 

 is constantly contracting, extending, twisting and turning, to 

 the distraction "of the observer, thus rendering observation 

 -difficult and tedious. 



The newly hatched young is a small, cylindrical, stumpy, and 

 lively person, swimming about briskly and having fully developed 

 jaws in constant motion, as if practising this most important life- 

 function. 



The extreme size of an adult Proales gigantea measures 508 /x 

 (l/50th of an inch) when extended. The toes measure 13"5/x 

 (l/1875th of an inch), and the small tail 68 /i, (l/370th of 

 an inch). The eggs are 102 /x (l/250th of an inch) long by 68 />t 

 (l/370th of an inch) wide, and the newly hatched young measures 

 176 ytx (l/145th of an inch) in length, 



I am indebted to Mr. F. R. Dixon-Nuttall for the excellent 

 figures illustrating this paper (PI. 24). 



As so little seems to be known of this parasitic Rotifer, 

 I determined to place some under observation, and work out 

 as much as possible of their life-history. This Club has always 

 been interested in pond-life, so I have concluded that the following 

 notes would be of interest to its members. 



I started by placing good clusters of the snails' eggs in com- 

 pressors, keeping them submerged in the trough, except when 

 iDoing examined under the microscope. I found this plan 

 unsuccessful, for the Rotifers died in about two days, together 

 with the embryo snail, although the water was kept fresh by 

 the frequent use of the pipette. I then tried thin troughs, taking 

 a cluster of eggs, not thick that is, the separate eggs were not 

 superimposed and marked off seven, each one numbered on a 

 diagram kept by my side during the days they were under 

 observation. Notes were taken seven or eight times each twenty- 

 four hours. All the eggs contained a good healthy embryo in 

 almost constant motion, turning round and round in the fluid 

 contents. Four of them were clean that is, no Proales were 

 present. The other three, Nos. 1, 6 and 7, had each one good, 

 healthy Proales, as if just arrived, and the small hole of entrance 

 could be seen. One I saw nibbling at the outside : a little later it 

 had got just half-way in, and it was very interesting, even amusing, 

 to see it wriggling through a hole which was much smaller than 

 itself, and looking for some time as if it could neither get forward 



