ZOOLOGY AND BOTANY, MIOKOSCOPY, ETC. 45 



(1) Even after accomplished impregnation, the above reagent hinders 

 the normal conjugation of the male and female nuclei. They form division- 

 figures for themselves and divide, but not normally. (2) Maturation and 

 fertilization are associated with fundamental protoplasmic changes. The 

 ovum-nucleus becomes differentiated into fibrils only in the fertilized egg, 

 and the sperm-nucleus in an unripe ovum remains either wholly unchanged 

 or becomes a watery vesicle. Hertwig raises the further questions (a) of 

 the possibility of fractional fertilization, and (6) as to the actual factors by 

 which the two nuclei are brought together. 



Importance of Sexual Reproduction for the Theory of Selection.* — 

 The main aim of Prof. A. Weismann's recent essay on this subject is to 

 establish the position that the process of sexual reproduction is the prime 

 agent by which all the varied differentiations of the complicated phyla of 

 the Metazoa have been brought into existence. It is urged that pecu- 

 liarities acquired by the parent are not transmitted to the offspring, and 

 that the hypothesis that such acquired peculiarities are transmitted is not 

 necessary for the explanation of the known phenomena of heredity. 

 Characters can only be said to be acquired, the origin of which is due to 

 external influences ; if these cannot be transmitted, it is clear that those 

 only can which were present in the germ at the time of its formation. 

 " There are no facts which really prove that acquired characters can be 

 inherited, although many attempts have been made to render such a suppo- 

 sition plausible " ; the fact that children of civilized parents, if isolated, 

 show no trace of a language, is cited in this connection. As against the 

 well-known experiments of Brown-Sequard — the hereditarily epileptic 

 guinea-pigs — it is urged that epilepsy is no morphological peculiarity, but 

 a disease. If the epilepsy be due to a microbe, then we can imagine that 

 the microbe might be transmitted with the sperm- or ovi-cell. 



The germ-plasma, though immensely complex in its finest structure, has 

 a remarkable power of persistence ; as it can remain unchanged it is obvious 

 that it is not easily to be modified. Hereditary individual varieties are to 

 be explained by the fusion of two antithetic germ-cells, or possibly nuclei 

 only ; the process of mingling is the cause of the occurrence of hereditarily 

 transmissible individual peculiarities, and it is the production of these 

 peculiarities which it is the office of amphigonic (or sexual) reproduction to 

 effect. 



This " startling conclusion " is further elaborated, and is shown to be 

 consistent with a large number of known facts, and accepted generalizations. 

 The author considers that he has plainly shown that the selection theory 

 is by no means incompatible with the conception of the continuity of the 

 germ-plasma, and that he has made sexual reproduction to a certain extent 

 comprehensible. 



Chemical Comparison of Male and Female Elements.f — Prof. O. 

 Zacharias has obtained some interesting and suggestive restilts from the 

 micro-chemical comparison of male and female elements in Characege, 

 Mosses, Ferns, Phanerogams, and — Amphibians. In the cases investigated 

 the male cells were distinguished by their small or absent nucleoli and by 

 their rich content of nuclein, while the female elements exhibited a poverty 

 of nuclein, an abundance of albumen, and one or more nucleoli more or 

 less large in proportion. The latter were not distinguishable from the 



* Weismann, A., ' Die Bedeutung der Sexuellen Fortpflanzung fur die Selektions- 

 Theorie,' 8vo, Jena, 1886. Cf. Prof. H. N. Moseley in « Nature,' xxxiv. (1886) pp. 629-32. 



t Biol. Centralbl., vi. (1886) p. 250 (Ber. 58 Versamml. Deutsch. Naturf 

 Strassburg, 1885). 



