ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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the iron been absorbed. Cuenot, in repeating the experiments, first fed 
cockroaches for six weeks on food devoid of iron, and still found that 
the Prussian blue reaction developed in the intestine after treatment 
with ferrocyanate and acid. Metalnikoff noticed a similar fact, but 
stated that the intensity of the colour was much less than when the 
insects were previously fed with iron salts ; Cuenot was unable to notice 
any difference in the two eases. Cuenot next fed the cockroaches with 
flour mixed with lactate of iron, and succeeded in obtaining a clear blue 
reaction in the mid-gut. He believes that in Metalnikoff’s experiments 
the cockroaches probably did not really swallow the iron salt. The 
result is therefore to confirm the earlier conclusions. Cuenot also be- 
lieves that the hind-gut has some iron-regulating function, such as that 
somewhat hypothetically attributed to the vertebrate liver. 
Digestion in Cockroaches.* — Herr Alexander Petrunkewitsch pub- 
lishes a preliminary note of his researches on this subject in Periplaneta 
orientalis and Blatta germanica. He finds that absorption takes place 
freely in the crop but not in the gizzard, and only to a slight extent in 
the mid-gut. It occurs also in the caeca and in the thin-walled region 
of the intestine. He finds that the whole digestive tract is densely per- 
meated by tracheal tubes, and believes that the peritracheal cells have 
the power of absorbing food-substances, and so nourishing themselves 
directly. 
Mid-gut of Dragonflies.^ — Prof. D. N. Voinov describes the epi- 
thelium of the mesenteron in the nymphs of 2Eschna , and refers to the 
recent discussion of the same subject by Mr. J. G. Needham, J with 
whose results he is in general agreement. The mid-gut is not only the 
area of secretion, where vesicles of digestive juice are abundantly pro- 
duced, but it is also the area of absorption, and the two functions proceed 
at the same time. The “ peritrophic sac” is not a special secretory 
product of the anterior meso-enteric zone, but is formed by the entire 
mid-gut from the secretory cells. Phagocytosis is wholly confined to 
the amcebocytes of the blood. Excretion is effected by the Malpighian 
tubules and by the pericardial cells. The latter pass their products into 
the blood to bo eventually eliminated by the Maljnghian tubules. 
Condylopalama agilis Sund.§ — Dr. H. A. Krauss has a note on this 
species, which was founded by Prof. Sundevall, for a larval form obtained 
from the bark of a Brazilian tree. Krauss is of opinion that the larva 
was that of a species of Embia ( Olyntha ), most probably of E. nobilis. 
Colour-variation in Vanessa io and urtic8e.|| — Dr. Friedr. Urech 
discusses the nomenclature and characters of the artificially-produced 
colour varieties of these butterflies., He believes that the varieties show 
that there is a gradual evolution of colour, orange being replaced by red, 
brown, umber-brown, and finally black. This evolution takes place both 
in phylogeny and in ontogeny, and determines the appearance of the 
special colours of the varieties, external conditions such as variations of 
temperature having only an indirect effect. 
* Zool. Anzeig., xxii. (1899) pp. 137-40 (4 figs.). 
t Bull. Soc. Sci. Bucarest, vii. (1898) pp. 49-52, 472-93 (2 pis.). 
X Zool. Bull., i. No. 2. § Zool. Anzeig., xxii. (1899) pp. 147-8. 
|| Tom. cit., pp. 121-33 (3 figs.). 
