ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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concentration of the rays would have killed the cells. The rayed ectoderm 
cells multiplied till the ectoderm was thrice the normal thickness, and 
the amount of pigment was greatly increased throughout, but especially 
in the deeper layer. J. A. T. 
Temperature Sense in Frog’s Skin. — Ann Haven Morgan ( Journ . 
Exper. Zool ., 1922, 35, 83-112). The frog’s skin contains well-defined 
receptors for heat and for cold. The heat receptors have a comparatively 
long reaction time. They are stimulated by 39° C. to 43° C. ; the cold 
receptors at 10° C. This response to cold is immediate and becomes 
more vigorous as the cold is increased. The typical response to heat is 
an upward jerk of the leg. The typical response for cold is a rigidity 
and tenseness of the muscles, but there may be an upward ierk similar 
to that of the heat response. Responses to heat and cold may be 
separated from each other and from the tactile and chemical senses. 
J. A. T. 
Evolution of Claspers of Elasmobranchs. — W. Harold Leigh- 
Sharpe {Journ. Morphology, 1922,36, 191-8, 5 figs.). Continuation of 
the author’s interesting study of “ claspers.” The oldest Elasmobranchs 
(the fossil Glcidoselache ) have no claspers, and almost certainly no clasper 
siphons or clasper glands. The next fossils have a direct type of 
clasper. Possibly the clasper siphons were not yet evolved or were 
present only in a rudimentary form. Subsequently the scroll type of 
claspers appeared, suggestive of the Scylliidm. Probably these were 
accompanied by a clasper siphon. The Lamnidse are geologically more 
recent than the Scylliidm, and have progressed a stage further and 
evolved a clasper gland, at any rate in recent forms. Later the skates 
arrived and resemble those of recent times. J. A. T. 
Claspers and Associated Structures. — W. Harold Leigh-Sharpe 
{Journ. Morphol., 1922, 36, 199-220, 22 figs. ; 221-43, 19 figs.). 
Comparative studies of the claspers, clasper siphons, and clasper glands 
in Ghimsera and Gallorhyncus, Torpedo, Trygon , ' Spinax, Gestracion, and 
other types. J. A. T. 
Growth of Fishes in Relation to Temperature. — P. Audige 
{Complex Rendus Soc. Biol., 1921, 84, 67-9). Observations on Salmo 
irideus, Salvelinus fontinalis, Cyprinus carpio, C. auratus, and Scardinius 
erythrophthalmus, which show a correlation between the temperature 
of the water and growth. There are optimum temperatnres. Increase 
in size is not uniform, but by fits and starts. The most rapid growth 
is in spring and in autumn. Reproductive activity is a notable check, 
and the rate lessens with age. J. A. T. 
Situs Inversus Viscerum in Double Trout. — F. H. Swett {Anat. 
Record, 1921, 22, 183-99, 6 figs.). In double trout there is often 
situs inversus viscerum, but the correlation is not precise. The reversal 
of asymmetry does not seem to be a necessary consequence of the 
doubling ; it may or may not occur, depending on some other factor. 
Mirrow-imaging only occurs when the digestive tracts are fused at 
some point between the pylorus and the exit of the intestine from the 
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