ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
173 
The first polar nucleus may bo extruded along with a little plasma 
( Pyrrhocoris , Lampyris ) ; or a plasmic knob may bo protruded, but not 
extruded, and may unite again with the ovum, the nucleus remain- 
ing undivided ( Tenebrio) or dividing into’two, both of which re-enter the 
ovum ( Agelastica, Adimonia ) ; or, thirdly, it may be that tho first polar 
nucleus remains in the cortical plasma and there divides again ( Musca , 
Pieris , Bombyx , Lcisius , Bhodites). The second polar nucleus may be 
extruded ( Pyrrhocoris , Lampyris ), or it may be retained (except in the 
two last-named genera), but it does not redivide. 
The chromosomata of the female pronucleus may retain their indi- 
viduality, or they may fuse into a network. The first polar nncleus 
may remain undivided or it may divide. In the latter case there are 
four nuclei visible. Their transformations are compared. 
It can rarely be said that a polar body is actually lost. Only in 
Lampyris does this seem likely. The second may unite with the inner 
half of the first, or the three may unite. The second Thelyid very soon 
disappears, the first may persist until fertilization is accomplished, and 
may be surrounded with plasmic radiations. 
Henking accepts the conclusion that the first and second divisions 
of the spermatocytes are comparable to the divisions which form the first 
and second polar bodies. The ovum at the time of fertilization is 
relatively younger than the spermatozoon. Polyspermy is common, and 
does not seem to have evil effects. The head of the spermatozoon 
usually bends round towards the tail, and a clear substance near the 
bend is distinguished as the Arrhenoid ; it seems to be connected with 
the tail, and to be comparable to the Thelyid. The gradual changes of 
the male nucleus are described. Vejdovsky’s observations on Bliynchelmis 
are in remarkable accord with those of Henking. 
The author proceeds to discuss different kinds of plasmic radiations, 
the history of the Thelyid, the formation of the segmentation nucleus, 
colourless nuclei, the number of chromosomata. He has a very interesting 
comparison of the processes of fertilization in Insects, Protozoa, and 
Angiosperms. The question of reducing-divisions, so important in con- 
nection with Weismann’s “ Amphimixis ” ; the observations of Ischikawa ; 
the general problems of fertilization and heredity are also treated of. 
Henking does not depreciate the importance of the nucleus as a bearer 
of hereditary qualities, but he also believes in the importance of the 
plasma, and in the modifiability of the chromosomata by influences 
from the protoplasm. 
Wings of Insects.* — Herr C. Hoffbauer has studied the wings of 
Bornbus lapidarius , Pontia cratsegi, Colias brassicse, Musca domestica , 
Chrysopa perla , Panorpa communis, Acridium grossum , Cimex rufipes , and 
numerous Coleoptera. He has devoted his attention especially to the 
wing-covers and to the glands associated with them. The wing-covers 
are in structure very different from the posterior wings. The charac- 
teristic venation is absent, and the distribution of the tracheae is quite 
different. In fact, the author is inclined to maintain that the wing- 
covers are homologous with the lateral lobes of the neck-shield. He 
finds corroboration in the Ephemerid Prosopistoma. On this supposition 
* Zeitschr. f. Wiss. Zool., liv. (1892) pp. 579-630 (2 pis., 3 figs.). 
