ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
291 
the animal to lower itself through the water. The rhabdites form a 
sort of chain armour ; they can be discharged, and produce slime on 
coming into contact with the water. Planarians sometimes creep along 
on the under-side of the surface film. When planarians — e.g. Dendro- 
ccelum lacteum — are irritated, the gliding movement passes into one in 
which the body, with the head fixed to the substratum, is stretched 
fully and then contracted violently. All avoid the light. Some species 
dispose their long axis parallel to the direction of the current, the head 
facing up-stream — e.g. Planaria alpina, P . gonocephala, and Dmdromlum 
lacteum ; others — e.g. P. torva and Polycelis nigra — appear indifferent ; 
P. cornuta reacts but feebly. The food consists of small crustaceans, 
insect larvae, small worms, and sometimes dead animals, or even plants. 
The discharge of rhabdites entangles the prey. The proboscis is inserted 
into the victim. They can do without food for a year; the reproduc- 
tive organs disappear first. They are very sensitive to slight changes of 
temperature, but the range differs considerably. The slimy secretion 
renders ihem unpalatable, but they may be eaten by newts, sticklebacks, 
and certain carnivorous insect larva. A description is given of the 
British species, and a diagnostic key. J. A. T. 
Echinoderma. 
Heat Production and Oxidation in Echinoid Egg during 
Fertilization. — Cresswell Shearer ( Proc . Roy. Soc., 1922, Series B, 
93, 410--25). In this investigation an attempt has been made to 
measure the oxygen consumption of the egg of Echinus miliaris during 
fertilization and early development, and to compare it with the amount 
of heat ‘liberated by the egg at the same time. The oxygen consump- 
tion was measured by a special pattern of the Barcroft differential 
manometer ; the C0 2 output by the same instrument. The heat 
liberation was measured by use of the differential micro-calorimetric 
method. The fertilized egg in the first hour of development gave off 
roughly six to seven times more heat than the unfertilized egg, and 
consumed at the same time six or seven times more oxygen than the 
unfertilized egg. On the whole the heat liberation of the egg on 
fertilization rises steadily, reaching its highest point when segmentation 
has been completed and the free-swimming stage is reached. On 
fertilization a greatly increased liberation of chemical energy is brought 
about within the ovum, as is shown by the increased oxygen consump- 
tion and the greatly increased carbon dioxide output and heat liberation. 
As, however, the calorific quotient of the unfertilized and the fertilized 
egg-cell is approximately the same in both instances, little or almost a 
negligible quantity of this energy is expended in bringing about the 
visible morphological structure of the developing ovum. Ii is probably 
employed in keeping the living substance itself intact as a physical 
system. J. A. T. 
Species of Stichopus. — H. L. Clark {Bull. AIus. Comp. Zool. 
Harvard , 1922, 65, 39-74, 2 pis.). Critical discussion of the species 
of this genus of Holothurians, well represented by conspicuous forms on 
weedy and sandy bottoms in shallow water throughout the Tropics. 
