( 153 ) 
SUMMARY 
OF CURRENT RESEARCHES RELATING TO 
ZOOLOGY AND BOTANY 
(^principally Invertehrata and Cryptogamia), 
MICROSCOPY, &c., 
DJCUIDING ORIGINAL COMMUNICATIONS FROM FELLOWS AND OTHERS.* 
ZOOLOGY. 
A. VERTEBRATA Embryology, Histology, and General, 
a. Embryology. t 
Weismann's Theory of Heredity-! — Professor A. Weismann lias 
published au important explanation of his views, in answer to a recent 
criticism by Prof. Vines. The difficulty which led the critic to regard 
it as “ absurd to say that an immortal substance can be converted into 
a mortal substance ” is due to a confusion of two conceptions — immor- 
tality and eternity. It seems to Weismann to be incontrovertible that 
the Protozoa and the germ-cells of the Metazoa are in a certain sense 
immortal ; though we have to do with individuals of indefinite duration, 
it by no means follows that this duration is eternal, for these individuals 
must have had a beginning. Eternity, to express it accurately, is merely 
the negation of the conception of transitoriness. As was said years 
ago, the immortality of these cells is not absolute, but potential ; it is 
not that they must live for ever, as the gods of the ancient Greeks ; they 
can die — the greater number do in fact die — but a projiortion of them 
live on. Here, as elsewhere, life depends on metabolism, or a constant 
change of material ; that, then, which is immortal is not the substance, 
but only a definite form of activity. The cycle of life is like the circu- 
lation of water, which evaporates, gathers into clouds, and falls as rain 
upon the earth, always to evajYorate afresh. As in the physical and 
chemical properties of water there is no inherent cause for the cessation 
of the cycle, so there is no clear reason in the physical condition of 
unicellular organisms why the cycle of life, i. e. of division, growth by 
assimilation, and repeated division, should ever end ; and this charac- 
teristic it is which Weismann has termed immortality. 
If then this true immortality is but cyclical, and is conditioned by 
* The Society are not intended to be denoted by the editorial “ we,” and they do 
not hold themselves responsible for the views of the authors of the papers noted, 
nor for any claim to novelty or otherwise made by them. The object of this part of 
the Journal is to present a summary of the papers as actually published, and to 
describe and illustrate Instruments, Apparatus, &c., which are either new or have 
not been previously described in this country. 
t This section includes not only papers relating to Embryology properly so called, 
but also those dealing with Evolution, Development, and Reproduction, and allied 
subjects. X Nature, xli. (1890) pp. 317-23. 
