ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
23 
but that in mammals and probably in Sauropsida the mesoderm shares to 
some extent in making it. His present investigation shows that in man 
the notochord has certainly its main foundation in the endoderm. 
development of Vessels and Blood in the Embryonic Liver.* — 
Dr. P. Kuborn finds that the formation and the increase of the giant- 
cells in the embryonic liver of sheep are due to the extension of the 
vascular plexus. Nucleated prolongations grow out from the endothelial 
cells forming the walls of the vessels, increase the vascular channels, 
and give rise in so doing to giant-cells. The giant-cells form the walls 
of vascular cavities, also hyaline cells which become red blood-corpuscles 
(erythroblasts of Lowit), and part of the liquid in which these float. 
But when the embryos have attained a length of 3-4 cm., the process 
becomes more complicated, for within the giant-cells and beside the 
red cells which continue to be formed there, special htematid cells 
(“ hematies ”) appear. These are developed in the protoplasm of the 
giant-cell as little spherical corpuscles, impregnated with haemoglobin. 
They become more and more distinct from the cell-substance in which 
they arise, are eventually liberated, and join the colourless and red cells 
in the vascular cavity. 
Relation of Mesonephros to the Pronephros and Supra-renal 
Bodies.! — Dr. R. Semon has investigated this problem in embryos of 
Ichthyophis glutinosus. (1) The pronephros has a Malpighian body as 
well as the mesonephros ; and though a segmental constriction of this 
body is not demonstrable, there are some hints of segmental structure. 
(2) The pronephric Malpighian body is a diverticulum of the body- 
cavity ; those of the mesonephros are also secondarily constricted 
coelomic diverticula. (3) The mesonephric canals with their Malpighian 
bodies represent the second (dorso-lateral) generation of the pronephros 
and its Malpighian body. (4) The non-nervous (inter-renal) portion of 
the supra-renal bodies is nothing more than the distal poi tion of the 
Malpighian body of the pronephros, which has undergone great 
modifications — degeneration of the glomerulus and of the efferent canals, 
besides loss of the lumen. (5) The reproductive organ also lies in a 
diverticulum which was constricted off in the formation of the Malpighian 
body of the pronephros. The testicular network and the vasa efferentia 
in the male, the so-called medullary strands in the female, are 
anastomosing cavities derived from the original diverticulum. At first 
there was a connection with the Malpighian body of the pronephros, but 
after this was modified to form the inter-renal portion of the supra-renal 
body, the connection was with the Malpighian body of the mesonephros, 
itself a derivative of the pronephros. Sometimes, indeed, both 
connections persist. 
Development of TJrinogenital Apparatus of Crocodiles and 
Chelonians-t — Prof. R. Wiedersheim finds in Crocodiles and Chelonians 
undoubted signs of a pronephros. Rather late in development it under- 
goes degeneration and consists only of a few glandular canaliculi which 
open by ciliated nephrostomes into the most anterior part of the coelom. 
On either side, and near the pronephros there is a large vascular coil 
* Anat. Anzeig., v. (1890) pp. 277-82. f T. c., pp. 455-82 (8 figs.). 
X Arch. f. Mikr. Anat., xxxvi. (1890) pp. 410-68 (3 pis.). 
