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well be doubted whether there are many other animals. which 
have played so important a part in the history of the world as 
“the poor worm.” 
Studies in the Theory of Descent. By Dr. A. WeIsMann. Trans- 
lated and edited by RapHarn Metpoua, F.C.S. Part IT. 
On the origin of the Markings of Caterpillars, and on 
Phyletic Parallelism in Metamorphic Species. With six 
coloured plates. 8vo. London: Sampson Low & Co. 
188]. 
In the first portion of this work, which is announced to be 
completed in three parts, Dr. Weismann examined the phenomena 
of seasonal dimorphism in butterflies; in the second part now 
before us we have two essays with the titles given above. Of 
these, the former embodies the details of a careful study of the 
change of markings which the caterpillars of the Sphingide 
undergo in the course of their development. From a considera- 
tion of these, the author deduces certain laws of development, 
which are subject to modification through the influence of natural 
selection, and the necessity for protection, thus giving rise to the 
various markings observable in different groups. These varieties 
of colour and markings in the Sphingide, according to Dr. Weis- 
mann, have a distinct biological value, and can in every case be 
traced to the action of natural selection and correlation of 
growth. 
In his second essay, the author compares different groups of 
Sphingide in their three stages of larva, pupa, and imago, and 
argues that the modifications which are found to occur are due, 
not to any innate law of variation and development (which would 
affect all the stages pari passu, and produce ‘“‘a phyletic paral- 
lelism ” which does not exist), but to an adaptation to special con- 
ditions to which, in one or other of its stages, the insect is 
exposed. This is stated to be the case not only with Lepidoptera 
generally, but with all creatures which undergo a metamorphosis. 
No one but an entomologist well conversant with German 
would have ventured on a translation of this very interesting 
work, for the numerous technical terms which everywhere occur 
require a translator who has not only a knowledge of the lan- 
guage, but a really thorough acquaintance with the subject matter 
