SCIENTIFIC SUMMARY. 
213 
suckerless part became depressed, forming a furrow wbicb eventually gave the 
body a reniform appearance. The surface of the groove showed what appeared 
to be strise, but these were resolved by a high power into rows of little points 
which increased rapidly ; the furrow spread so as to form a ring round the 
body, and its points became converted into long thin cilia which began to 
oscillate gently. The suckers had then entirely disappeared, and after a time 
the body was flattened in a direction vertical to the ciliated belt, the cilia 
became more active, and the Podophrya moved through the water, turning upon 
itself, but with the part where the furrow originally appeared always in front. 
All these changes took place in about half an hour. The period of activity 
varies in length, and in returning to the motionless condition the Podophrya 
passes through a series of changes the reverse of those above described; the 
suckers appear first, then the body shortens and becomes broader, the 
vibratile cilia are gradually retracted and the body rounded, and in about 
twenty minutes the animal resumes its globular form with its surface covered 
with long suckers. The same individuals passed several times through this 
series of metamorphoses. M. Maupas regards Podophrya as an intermediate 
type uniting the Infusoria Suctoria with the Ciliata. 
Commensalism in Caterpillars. — Dr. Fritz Muller describes a curious 
instance of commensalism in two larvae of some unknown Lepidoptera. He 
says the larger caterpillar, which has a red head, aud is protected from 
enemies by long, branched, white stinging hairs, lives on mulberry and 
other trees. Like other protected caterpillars it is light-coloured and sits on 
the upper surface of the leaves. The second caterpillar is a little blackish 
fellow, and lies across the back of his larger companion, concealed among the 
stinging spine-like hairs of the latter. When taken oft he went back to his 
original place immediately. In order to photograph the two animals Dr. 
Fritz Muller stupefied the large one with aether, which caused its death in 
about two days. The smaller caterpillar then quitted his post, and took up 
his abode on a second specimen, the place that he had occupied on his former 
host, having a pale and worn appearance. The smaller caterpillar stretches 
down from his position of vantage among the spines of the larger, and eats 
little holes in the leaf on which the latter rests. — Zool. Garten , 1877, p. 67. 
Fauna of Lake Gokcha. — The study of the faunas of isolated sheets of 
water promises to furnish some of the most striking direct confirmations of 
the theory of the origin of species by descent with modification, and all 
records of such investigations must be regarded as of much importance. 
Lake Gokcha, on the fauna of which Professor Kessler has lately published 
a memoir in the u Memoirs of the Society of Naturalists of St. Petersburg,” 
is one of these interesting localities, being situated in the Caucasus, at a 
height of 6,419 ft., and entirely surrounded by lofty mountains, through 
which only a small river carries off its surplus waters. Its surface occupies 
about 660 square miles, and its general depth varies between 150 and 
250 ft., but in one part it reaches 361 ft. In this lake Professor Kessler 
found Spongillce to be exceedingly abundant. The commonest worm is 
Nephelis vulgaris ; the Crustacea are represented by numerous Entomostraca, 
and by a single species of Gammarus ; the Gasteropod mollusca are all well- 
known European species ( Limnceus stagnalis , ovatus and auricularius and 
Planorbis carinatus ) ; and the Bifo viridis and a local variety of the 
