ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
169 
undertaken with success, so we may hope to control the trophic and 
aggregation phenomena of ontogeny. By experiment alone can the 
causes of the developmental processes be determined. 
Development of Red and White Blood-Corpuscles.* — Dr. Fr. Saxer 
gives a preliminary.note of his researches on this subject. Both red and 
white corpuscles owe their ultimate origin to “ primary wandering-cells,” 
which appear at an early stage, and are not connected with the connective- 
tissue elements. These wandering-cells, by direct division, or by pluri- 
polar mitosis, may become converted into multi-nucleated giant-cells. 
The nuclei may fuse, producing cells with lobed nuclei (megakaryocytes) ; 
or, by division, cells having the primitive characters may be reproduced. 
The primary cells, or these secondary ones, divide either by direct or 
indirect nuclear division, and form transition cells with simple nuclei. 
These transition cells are also migratory, and penetrate to all parts of 
the embryonic body. In the early stages of development they give rise 
only to red corpuscles, but later also to the white. 
Metazoan and Metaphytic Reproductive Processes.! — Prof. Con- 
way MacMillan comments severely on Dr. Beard’s theory regarding the 
essential resemblance between metazoan and metaphytic reproductive 
processes. lie has his own views on the matter. First, we must be 
clear as to the difference between palingenetic spores, e. g. in Bacillus 
anthracis, and coenogenetic spores, which are always subsequent to a 
sexual process. Then we may see that the metaphytic coenogenetic 
spore is a homologue of the metazoan blastomere. “ The syngamete of 
the metaphyte or of the metazoan may develop in one of two ways — 
directly, into an organism like the parent, or indirectly, into a group of 
isolated blastomeres, spores, or into a single spore-mother-cell or (in 
plants only) into spore-mother-cells plus sterilised spore-mother-cell 
homologues.” In plants the group of isolated blastomeres (coenogenetic 
spores) is laid hold of by natural selection, and improved and integrated 
into a sporophyte. In animals this does not happen. The author works 
on to show that “ sporophytisation is as essentially a plant character as 
cephalisation is an animal. The one is an expression, in the organism, 
of the static life ; the other of the dynamic.” 
Development of Pancreas in Man.J — Dr. A. Jankelowitz finds in a 
human embryo of the fourth week that the human pancreas arises from 
three rudiments, which are at first quite separate, — a dorsal which is 
associated with the epithelium of the primitive duodenum, and two 
ventral, which arise from the groove-shaped rudiment of the ductus 
clioledochus. 
Dentition of the Dog.§ — Dr. H. W. Marett Tims notes among the 
results of his study of the development of the teeth in the dog the fol- 
lowing conclusions : — (1) The evidence of a pre-milk dentition in 
modern mammals is insufficient ; (2) a lingual downgrowth of the dental 
lamina represents a post-permanent series, and occasionally gives rise to 
a functional tooth ; (3) in the dog, the first premolar and the molars 
belong to the so-called permanent dentition. 
* Anat.'Anzeig., xi. (1895) pp. 355-8. f Tom. cit., pp. 439-13. 
X Arch. f. Mikr. Anat., xlvi. (1895) pp. 702-8 (11 figs.). 
§ Anat.“Anzeig., xi. (1896) pp. 537-46 (5 figs.). 
