ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
41 
such theory, are hardly to be expected to admit that the botanists may 
have obtained a deeper insight into the phenomena of plant-development 
than they believe themselves to have of those of animal-reproduction. 
Dr. Beard’s object appears to be to consider the following problem : — 
Assuming an antithetic alternation of generation to take place in meta- 
zoan development with aposporous formation of the sexual generation in 
most if not in all cases, to show what bearings such a conception may 
have on the interpretation of certain phenomena that occur in the 
maturation of the sexual products ; and, as a corollary to all this, it has 
been deemed necessary to enquire into the nature of the processes in- 
volved in the conjugation of the Protozoa. The result surprised the 
author, for he came to recognise the prevalence of one primitive mode 
of reproduction for the whole of organic nature, and this is of such a 
character that an alternation of generations becomes absolutely essential 
to its being carried out. Mr. J. A. Murray was associated with Dr. Beard 
in the chapter on the reducing division in Metazoan reproduction. 
Taking the results of various writers, they explain their researches as 
showing, for the case of the Vertebrate, at any rate, how the gametozooid 
arises from an aposporous tissue within a larval or asexual generation 
resulting [from the segmenting of the egg. It is suggested that the 
pole-mesoderm cells of Hatschek may be interpreted as representing 
spore-mother-cells which have undergone no reduction. Passing to a 
consideration of the conjugation of the Infusoria and the meaning of the 
processes involved, Dr. Beard considers the work of R. Hertwig and 
of Maupas. The primitive form of sexual reproduction or conjugation, 
apart from fission, was from its very nature bound up with an asexual 
process, or spore-formation, leading to the reduction of the previous 
reduplication of chromosomes. This very primitive antithetic alterna- 
tion of generations still exists, and is bound to remain in a more or less 
modified form in both plants and animals, in consequence of the dupli- 
cation which results from any conjugation. 
Spermatogenesis in Birds.* — Mr. J. E. S. Moore finds that the 
spermatogenesis of Birds supports in every way the conclusion, first put 
forth by Strasburger, which is at present gaining ground — that the pro- 
cess of numerical reduction in the chromosomes is not brought about by 
any division at all, and is similar for both animals and plants. 
Chromatin-Reduction in the Maturation of Ova and Spermatozoa.! 
— Dr, 0. vom Rath has collected and extended his observations on the 
reduction-processes. A comparison of those which occur in maturation 
of the ovum in Copepods with those in the spermatogenesis of Gryllo- 
talpa and Salamandra reveals a remarkable congruence. The author 
agrees rather with Riickert than with Ishikawa and Hmcker, but he 
holds that both maturation divisions are reducing-divisions, while 
Riickert holds that only the second is of this nature. It does not seem 
to be at present possible to decide this question. 
In all the cases of spermatogenesis and oogenesis which Vom Rath 
has observed, the quadruple groups ( Yierergruppen ) arise before the 
period of maturation in the same way. In the coil-stage two segments, 
* Rep. Brit. Ass., 1895, pp. 735 and 6. 
t Arch. f. Mikr. Anat., xlvi. (1895) pp. 168-238 (3 pis.). 
