ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
23 
kinds are unconnected by transitional forms and behave differently under 
the influence of warmth. 
Phagocytosis by Blood-Plates.* * * § — Dr. S. Kamon y Cajal has demon- 
strated the occurrence of phagocytosis (of carmine particles and Bacteria) 
in the blood-plates of lower Vertebrates, such as the frog. 
Function of Interstitial Cells of Testis. f — Herr J. Plato has 
studied the testes of cat, mouse, &c., and has been led to the conclusion 
that, in the cat at least, the interstitial cells serve for the absorption and 
storage of fat, which is used in the nutrition of the ripening spermatozoa. 
He has discovered fine canals, which conduct the stored material to 
where it is used up. 
Regeneration of Mucus Epithelium of Intestinal Tract in Amphi- 
bia.! — Dr. C. Sacerdotti finds that in the oesophagus and stomach of the 
frog and in the intestine of the newt, the mucus epithelium is formed 
from elements which acquire their function of mucus-secretion before 
they reach their final position. Their centre of formation is in the 
deeper strata of the gut-wall, whence the elements reach the surface, 
partly by the wearing off of the old superficial epithelium, partly because 
they are pressed out by younger elements which arise beneath them. 
Thus he confirms Bizzozero’s conclusion that the mucus-cells are specific 
elements, and that the intestinal epithelia do not usually arise where 
they are seen in their fully differentiated state. 
y. General. 
Sexual Dimorphism and Variation^ — Prof. J. Kennel gives the 
following summary of an interesting essay : — 
Male and female are normally similar in those external characters 
which are not in direct relation with reproductive functions (sexual 
homomorphism). 
The two sexes usually show parallel variations, a parallelism which 
may be due to the similar action of similar causes, or may be the result 
of transference from one sex to the other. 
Deviations from previous characters may be gradually increased, or 
they may be of sudden origin (saltatory variation). 
Variations are not planless, but arise according to the species in 
definite directions, not always in one, yet not in very many. It is thus 
that varieties and new species arise. 
Variations in a definite direction may sometimes be increased in a 
high degree, even beyond the limits of utility and advantage (evolution- 
tendencies). 
Conditions may arise in which external organs regress or degenerate 
to the advantage of reproductive function. This is especially true of the 
female sex, in which the reproductive function demands more material 
sacrifice and more complex substances. Thus arises “individually 
conditioned ” sexual dimorphism. 
At first this need not be transmitted, as it arises from similar causes 
* Ann. Soc. Espan. Hist. Nat., v. (1896) pp. 5-12 (2 figs.), 
t Arch. f. Mikr. Anat., xlviii. (1896) pp. 280-801 (1 pi.), 
j Tom. cit., pp. 359-69 (1 pi.). 
§ Schriften Nat. Ges. Jurjeff (Dorpat) ix. (1896) pp. 1-64. 
