32 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
rations are much reduced, and may form only two little pockets on the 
first segment. 
Aphelopus melaleucus appears to be pretty common ; in Wimereux 
and at Meudon the sac which contains the larva is of a blackish colour, 
and not yellow, as in the Luxembourg Garden. This colour is evidently 
])rotective of the more numerous individuals living on T. uhni, the 
abdomen of which is black, and is probably due to heredity in the 
others. It is possible that Aphelopus presents varieties in the different 
species of Typhlocyha which it infests. 
Phytophagous Habits of the Larva of Friganea.* — Dr. D. Levi- 
Morenos finds that the larvte of different species of Friganea (Neuro- 
ptera), usually stated to live on aquatic flowering plants, comparatively 
seldom feed on the green parts of the plant, though occasionally on the 
root and epiderm. He finds, on the other hand, the alimentary canal 
loaded with diatoms of many different species. From some of these 
the endochrome is entirely removed in the process of digestion, while 
others remain comparatively intact. 
Embryology of Blatta Germaiiica and Doryphora decemlineata.t— 
Mr. W. M. Wheeler gives a detailed account of his observations on the 
development of the cockroach and the potato-beetle. In all the details 
of their history the two forms differ strikingly, but their main ontogenetic 
features are as strikingly similar. 
After an account of the ovaries and modes of oviposition the develop- 
ment of the egg is described as far as the formation of the blastoderm ; 
though the author adds something more to our knowledge of the copula- 
tion of the pronuclei than Blocbmann, he considers that the process 
must be studied in Arthroj)od eggs with more evenly compact yolk than 
those of the Orthoptera, the numerous cracks and fissures in which 
render the observation of delicate internal processes exceedingly difiicult, 
if not impossible. The nuclei, at one time in the yolk, all appear to 
rise to the surface to form the blastema and reinforce it in its formation 
of the blastoderm. 
The author maintains that a portion of the chromatin of the insect- 
egg visibly survives in the decomposition of the germinal vesicle, and 
can be traced through the divisions resulting in the formation of the 
two polar globules into the cleavage-nucleus and its descendants. In 
other words, there is no moment when the nucleus ceases to exist as 
nucleus. Particular attention was paid to the determination of the 
paths of the pronuclei and cleavage-nucleus in Blatta, and experiments 
were made on the possible efiects of gravitation. The conclusion arrived 
at is that the force of gravitation has no perceptible effect on the de- 
velopment of the eggs of Blatta ; their highly differentiated eggs, utterly 
unable to revolve in their envelopes like the eggs of birds and frogs, 
have their constituents prearranged, and the paths of their nuclei pre- 
determined with reference to the parts of the embryo. The spherical 
form of the crustacean egg, as opposed to the oval shape of the great 
majority of insect-eggs, will be a great obstacle in the way of extending 
this generalization to the lower group. 
* Notarisia, iv. (1889) pp. 775-80. 
t Journ. of Morphology, iii. (1889) pp. 291-372 (7 pis.). 
