n Mr. VV. Low Sarjeant on 



much more beautiful object than when the whole plant is green, 

 as we find it in the ordinary summer gatherings. Melicerta 

 rlm/ens and Stephanoceros FAchornii are two good forms which 

 may be found here. These are, of course, attached to the weeds, 

 more particularly to the submerged fine leaves of the water 

 crowfoot and the star-weed. Here also Floscularia ornata, 

 (Ecistis crystallinus, and several other tube-dwelling rotifers may 

 be found ; Actinospherium, which is like a very large Actinophrys 

 sol, is generally abundant, and is a most beautiful object. 

 Daphnia, Cyclops, Hydra viridis, and vuhiaris, several free- 

 swimming rotifers, two or three species of Vorticella, and many 

 kinds of Infusoria are also to be taken. 



Some of the tube-dwelling rotifers, such as Stephanoceros, 

 Floscularia, &c., on account of their extreme transparency, are 

 at times very difficult to find ; a piece of weed having many 

 specimens attached to it may be passed over as valueless if 

 simply held up to the light and examined. The best method of 

 detecting these delicate forms is to use a black-ground illumina- 

 tion, which may very easily be accomplished if the bottle is large 

 enough by placing the finger or fingers at the back of the bottle, 

 and then holding it up rather obliquely to the brightest light 

 obtainable. The curvature of the glass bottle condenses the 

 marginal rays of light on the object, while the finger stops out 

 the central rays, or, if the bottle is small, a piece of stick or any 

 other opaque object proportionate to the size of the bottle will 

 answer. One or two trials will enable any one to obtain a dark 

 background in this manner, and it is surprising with what ease 

 organisms can be detected that are practically invisible by 

 transmitted light only. 



Upon dipping in a pond near Tuubridge Wells last Easter, I 

 came upon Valvo.v in enormous numbers, a large proportion of 

 which contained the orange-coloured young. This orange- 

 coloured variety is probably a kind of winter or resting stage in 

 the development, somewhat similar to the statoblasts of the 

 Polyzoa. I then noticed what I have often before obsei-ved, 

 although never in so marked a manner, how very locally, even 

 in a pond of small area, its inhabitants are sometimes con- 

 gregated. In one part of this pond there were thousands of 

 Volvox in every ounce of water, — in fact the water appeared 

 green with them, whilst a few paces farther on, after straining 

 several pints of water through my collecting-bottle, I could not 

 obtain a single specimen either of Volvox or any other form of 

 life. A short distance further the water was teeming with 

 Daphnia, Cyclops, and other similar forms, but no Volvox. I 

 mention this to show how necessary it is in collecting not to rest 

 satisfied with dipping in one place only, but to try in various 

 parts of a pond. 



