158 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Karyogamic Reduction in Oogenesis.* — M. A. Lameere pnblislies 
an abstract of a memoir wbicb lias for its object the demonstration of 
the view that the polar globules cannot represent the elements eliminated 
from the egg to be replaced by the nucleus of the spermatozoon. Prof. 
E. Van Beneden has lately shown that in the division of the spermato- 
gonia of Ascaris megalocephala there is an expulsion of polar globules, 
and he comes to the conclusion that the ripe ovum and the spermatozoa 
are homodynamous. The author reports the discovery, in the narrowest 
portion of the ovary of the just -mentioned worm, of residual corpuscles, 
identical in structure and probably in origin with those of spermato- 
genesis. After a number of direct divisions the nuclei of the primitive 
ova exhibit kinesis, and two chromatic loops are expelled, which appear 
to together constitute a residual corpuscle. These bodies are at first 
hyaline. The author concludes, therefore, that the ovum and the 
spermatozoa undergo, in a parallel manner and under the form of the 
expulsion of residual corpuscles, the karyogamic reduction which 
indicates the formation of pronuclei. 
Karyokinesis in Larval Amblystoma.j* — Mr. J. A. Ryder reports 
that a species of this genus of Urodeles affords by its embryos ex- 
ceedingly interesting subjects in which to study karyokinesis and 
indirect cell-division. Nuclear spindles could be easily detected in all 
the tissues of the body in the greatest variety of stages. This creature 
is an excellent subject for histological teaching, as it illustrates the fact 
that karyokinesis is universal and holds with respect to all the tissues 
during the early stages of development. As the cells are very large, 
the spindles are also so ; the filaments of chromatin are very large, 
thick, and sharply defined, so that all the phases of nuclear meta- 
morphosis may be readily traced with moderate powers. 
To prej^are the embryos, they were killed and hardened with corro- 
sive sublimate or Kleinenberg’s picro-sulphuric acid. After hardening 
and washing in alcohol, the embryos were stained in toto in a dilute 
solution of hmmatoxylin, Kleinenberg’s or Delafield’s answering admir- 
ably ; the chromatin threads being dee2)ly stained with the dye contrast 
with the rest of the substance of the cells. Sections should be made in 
transverse as well as in vertical and horizontal planes. 
Leucocytes in Tail of Tadpole. J — Herr A. Looss in a memoir 
discusses the share taken by leucocytes in the destruction of the tissues 
of the tail of the tadpole. It would appear that Metschnikofif’s con- 
clusions have been given too wide a bearing, for in the metamorphosis 
of the frog they play a much more subordinate part than in the Diptera 
and invertebrate animals generally. The leucocytes would seem to 
form a kind of reserve force for the animal body which only comes into 
prominent use if the organism is unable, with the ordinary means at its 
disposal, to perform certain extraordinary duties, or to struggle against 
special difficult relations. Herr J. H. List remarks that we have in the 
doctrine of Phagocytes another example of a generalization made without 
sufficient critical observations in Invertebrates and Vertebrates. 
* Bull. Acad. Roy. de Belgique, lix. (1889) pp, 712-4. 
t Amer. Natural., xxiii. (1889) pp. 827-9. 
; Biol. Ceutralbl., ix. (1889) pp. 595-9. 
