712 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
order, or even class, which cause the appearance of variations, are, in 
the beginning, due to the primary (direct or indirect) factors of evolution 
(Neolamarckism), while the final stages are due to the secondary 
factors, segregation and natural selection (Darwinism). 
Biology of Lepidoptera.* — Dr. A. Seitz publishes the first instal- 
ment of an account of the general life of Lepidoptera. He speaks first 
of the manner in which Lepidoptera are distributed ; of cosmopolitan 
forms, like Pyrameis cardui , which flies swiftly and far, has a long life 
and much hardiness, and is moreover able to rest with spread wings 
upon the water ; how others stand or fall with the presence or absence 
of the food-plants on which their monophagous caterpillars live ; what 
advantages there are in acquiring the habit of polyphagy ; how manifold 
are the means of transportation, e. g. in railway carriages and ships ; 
how some forms are constitutionally prone to wander; and how the 
family of Psychidae, in spite of their wingless females, has come to be 
very widely distributed. 
In the second chapter he relates his own observations and those of 
others on the active wanderings of Lepidoptera over land and sea, singly 
or in swarms, as adults or as caterpillars, and after discussing the 
various reasons for this, falls back on the belief in a genuine “ Wander- 
trieb.” Then follows a criticism of generalizations in regard to geo- 
graphical distribution, and a constructive attempt to improve these. He 
discusses the factors determining the distribution of Lepidoptera in 
continents, countries, and localities ; submits a number of phsenological 
and geographical tables ; and notes the characteristics of the Ethiopian, 
Indo- Australian, and Neotropical fauna. An account is given of a 
restricted area of woodland in South Brazil, where the great majority 
of the insects were blue (not the Lepidoptera alone, but Coleoptera, 
Hemiptera, and Diptera), although but a few miles off a red colour was 
dominant, and he argues that the facts could not be explained as due either 
to mimicry or to general protective resemblance. In the fourth chapter 
the influence of climate and weather on Lepidoptera is discussed, with 
abundant details as to the effect of mild winters and hot summers, rain 
and wind ; and even the periodicity of the sun-spots is not forgotten. 
New Excretory Organs in the Silkworm.f — Prof. E. Verson de- 
scribes fifteen pairs of cutaneous glands in the larva of Bombyx. In the 
thorax there are two pairs to each ring, one set lying slightly in front of 
or above the stigmata, the others at the external base of the appendages. 
There are nine pairs in the abdomen with somewhat analogous positions. 
In the larva about to be hatched the glands measure only 0 * 02 mm. by 
0*03 mm., but in later stages a maximum diameter of 3 mm. may be 
attained. 
A well-developed gland has an ample cavity, containing some 
granular material, surrounded by a broad spongy cortex, and leading 
into a short excretory canal with a large covering cell or with several. 
In the young larva, however, the future glands are seen to be true cells 
with large nuclei, and Verson maintains that the cortex of the gland is 
derived from the protoplasm of the primitive cell, while the cavity 
* Zoolog. Jahrb., v. (1890) pp. 281-343. 
t Bull. Soc. Entomol. Ital., xxii. (1890) pp. 3-29 (4 pis.). 
