HARD WICKE' S SCIENCE-GOSSIP. 



same bottle is immersed in cold instead of hot water, 

 contraction of the enclosed air will consequently 

 result, and the membrane will be drawn in more or 

 less deeply concave. Not only does this law apply to 

 gases, (which are most sensible to it), but also in a 

 less degree to fluids, and less still to solid bodies as 

 above remarked. 



Another good way of illustrating the same law, 

 and perhaps the most obvious of all the preceding, 

 is to obtain a thin glass vessel, with a 

 double communication, that is to say with 

 two mouths. By suction, the air is drawn 

 through this vessel by the widest opening, 

 which is then well-corked, and the whole 

 immediately placed under boiling water ; from 

 the small unstopped aperture, numerous small 

 bubbles of air will issue in rapid succession, 

 due to the heat causing the contained air 

 to dilate. When, after the bottle has been 

 immersed a minute or two, the body is held 

 out of water, considerable contraction of the 

 expanded air will ensue, and consequently an equiva- 

 lent quantity of water will be drawn in ; if after 

 remaining thus a short time, the vessel is taken out 

 (still inverted) of the fluid, further condensation of 

 the air will result, and small bubbles will continue to 

 be drawn through the water, until the bottle and its 

 contents have attained a temperature alike to that 

 of the surrounding atmosphere (Fig. 2). The water 

 drawn in and the remaining air will be nearly 

 approximate to the air it first contained. 



Upon this law is based the construction of the 

 "air-thermometer," and thermometers generally. 



Henry E. Griset. 



NOTES ON THE RECENT OCCURRENCE 

 OF SOME FOREIGN SPECIES OF ROTI- 

 FERA IN ENGLAND. 



By Percy G. Thompson. 



AT a period like the present — when, owing to the 

 impetus given to the study of rotifers by the 

 publication of Hudson and Gosse's elaborate mono- 

 graph, new forms are continually being brought 

 before our notice — there is danger that the often 

 long-since described forms of foreign authors may 

 drop out of the local worker's memory, or be passed 

 over as of unlikely occurrence to his own research. 

 It is, however, of prime importance that these 

 earlier forms should be continually kept in vivid 

 remembrance, and that, if happily met with, they 

 should without, delay be recorded as additions to our 

 British list, and, if possible, our knowledge of their 

 structure extended. 



Mr. George Western has done useful work in this 

 direction in. demonstrating the presence in our own 

 country of CEcistes viucicola, Kellicott, which makes 

 its home in the gelatinous matrix of certain fresh- 



water algae (Gloiotrichia and Chaetophora), and 

 which up to last year had been recorded solely from 

 America ; Mr. Western has also found the probable 

 male of this (Ecistes. 



The present paper is intended as a further con- 

 tribution towards this extension of our indigenous 

 rotifer-fauna by the inclusion of certain species hitherto 

 only known as foreign. 



Aiaircca valga, Ehrenberg. The pretty little 



Fig. 3. — Atuiriea valga. 



Side view, taken obliquely from the right side : 

 a, ventral plate. 



Anurasa which I regard as identical with the above 

 species, I have met with on several occasions and in 

 considerable numbers from shallow ponds on Leyton 

 Flats, near Snaresbrook. It is also recorded (but 

 without specific identification) as found by the 

 members of the Quekett Club on several of their 

 excursions to localities round London, and I have 

 had it sent up to me from the Isle of Wight, so that 



Fig. 4. — Anuria valga. Dorsal view of empty lorica, showing 

 tesselation : a, lateral edge of ventral plate. 



the form is probably widely distributed through this 

 country. It will be well to examine in some detail 

 the anatomy of my Snaresbrook specimens, 'and to 

 conclude with a few remarks on the questionable 

 right to specific distinctness of this form and of 

 certain of its near allies. 



The lorica scarcely differs in its size and propor- 

 tion from that of the well-known A. aculeata (Ehrb.). 

 Like the latter, it consists of two plates, a larger 

 slightly elevated dorsal, and a fiat ventral plate of 



I 



