ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
395 
the evidence of the condition of the nuclei represented at a particular 
moment still rests upon Prof. Wilson’s reputation as a histologist as 
completely as it could have done had he published the woodcuts only, 
or no figures at all. It seems certain that the best photograph, at 
present possible, does not show as much as can be seen by looking 
directly at a good histological preparation, so that it is not yet possible 
for the histologist to multiply copies of his evidence, in a form from 
wticli the subjective element is altogether excluded. There is still no 
way of testing a histological subject without direct examination of the 
object described. Prof. Weldon thinks that a careful drawing by a 
trained observer gives a better idea of appearances seen under the 
Microscope, than the best available reproduction by photograph can at 
present achieve. 
Spermatogenesis.* — Prof. K. von Bardeleben maintains that only the 
heads of spermatozoa arise from the spermatides, and these from the 
round,” darkly nucleated, peripheral cells (spermatogonia) by karyo- 
kinesis. The tails, and especially the axis-threads, arise from the cells 
with pale nucleus, which have their origin from, or are identical with, 
the supporting, basal, or Sertoli’s cells. The tails arise amitotically by 
outgrowth or disruption of these cells. Thus the two parts arise 
separately, and the thickened anterior end of the (hollow ?) axial thread 
unites with the posterior end of the vesicular or balloon-like head-rudi- 
ment, forming at the junction the so-called N ebenJcdrper. There is a 
distinct origin for the fertilising substance and the motile substance, 
and the originating elements may be termed head-cells and tail-cells. On 
this view the head corresponds to the ovum, the tail to follicle-cells or 
egg-envelopes. 
Development of Liver and Adjacent Parts.j — Prof. A. Swaen has 
studied in the rabbit the development of the mid-gut, liver, and pos- 
terior peritoneal cavity. The hepato-enteric cavity is a primitive 
formation, and nowise the result of a rotatory movement of the gut. In 
embryos of 10J-11 days this cavity is in its anterior portion a vertical 
cleft in the mesenteric septum along the right lateral wall of the gut ; 
it divides the fold into two portions, of which the right is the meso- 
lateral. Posteriorly, the cavity is an antero-posterior groove in the 
middle part of the mesenteric septum ; still further back it passes into 
a cul-de-sac. The rotatory movement of the gut modifies the situation 
of the hepato-enteric cavity and leads to the formation of a dorsal meso- 
gastrium. Prof. Swaen proceeds to follow out the intricate modifications 
of cavities and mesenteries, and describes the development of the lobes 
of the liver and of the abdominal veins and sinuses. 
Normal Hyperthely in Human Embryos.f — Dr. H. Schmidt gives 
an account of his observations on the occurrence of supernumerary 
mammary glands in human embryos. They occurred both above and 
below the normal glands, but were all localised in the upper pectoral 
region. He regards embryonic hyperthely as the normal condition. 
* Anat. Anzeig., xi. (1896) pp. 697-702. 
t Journ. de l’Anat. Physiol., xxxii. (1896) pp. 1-84 (3 pis.). 
t Anat. Anzeig., xi. (1896) pp. 702-11. 
