SUMMARY OF CURRENT RESEARCHES RELATING TO 
some cases be completely wanting, and this is especially so in Phjllo- 
dromia , a form which for many reasons is supposed to he very 
primitive. 
In those cases in which the mesoderm arises by a typical invagina- 
tion, the author does not regard the invagination as a gastrulation, but 
as a simple mechanical process, caused by an aggregation of cells at one 
point. Analogous processes may be cited, and insect embryology alone 
oilers sufficient examples ; organs may in some Insects be formed by in- 
vagination that are in others developed by wandering or immigration ; 
this idea offers an explanation of the as yet uncomprehended process of 
“ lateral gastrulation.” 
It is possible that we must look for the endoderm in the cells that 
disappear in the yolk ; if this be so the layer that forms the midgut of 
Insects is a neomorph, and if it be so we have the unpleasant result that 
Insects, in their adult stage, have no endoderm at all. Another explana- 
tion may be found in the supposition that, owing to certain causes, the 
endoderm does not become differentiated till very late ; but such a hypo- 
thesis as this has very little, if anything, to support it. 
The author promises a more detailed account of his studies. 
Alternation of Generations in Insects.* — Herr L. Anderegg dis- 
cusses the question of alternation of generations at great length. He 
begins with the fundamental constitution of matter, takes in a classifica- 
tion of the animal kingdom by the way, contrasts the inorganic and the 
organic, the plant and the animal, and does uot neglect to raise several 
vexed questions in passing, e. g. in regard to “ individuality.” Reaching 
the facts he states the case for Cynipidae, Phytophthira, Chermetidae, 
and Aphidae. That the parthenogenetic forms are part of the de- 
velopmental cycle, the author allows, but they are not, as Lichtenstein 
would have it, merely developmental stages, bearing to the sexual forms 
the same kind of relation that larvae bear to imagines. He agrees with 
Leuckart that the interpolated parthenogenetic individuals form equiva- 
lent generations, but will not accept the statement that they represent a 
heteromorphism of the species, as in seasonal dimorphism. The general 
conclusion seems to be that there is true alternation of generations in 
oak-Cynipidse and Phytophthira. It seems to us that the chief value of 
the memoir is to be found in the author’s concrete observations, in his 
summaries, and in the diagrammatic expressions of the complex life- 
histories, but not in the generalizations. 
Metamorphoses of Insects.f — M. le Capitaine Xamben continues his 
account of the habits and metamorphoses of insects, dealing with larvae 
of Paussidae, Pselaphidae, Silphidae, Trcgositidae, Lamellicornes, and 
Buprestidae. 
Relations between Colouring and Habit in Lepidoptera.ij:— Hr. M. 
Standfuss discusses the relations between the colouring of Palaearctic 
Macro-Lejudoptera and their habits. He begins by contrasting Rhopa- 
locera and Heterocera in which the difference in the position of the 
wings when at rest is well known to be associated with a difference in 
* MT. Nat. Ges. Bern. 1893, pp. 1-G9. 
t Ann. Soc. Linn. Lyon, xxxix. (1892!) pp. 135-94. 
X Vierteljahrschr. Nat. Ges. Zurich, xxxix. (1894) pp. 85-119 (8 figs.). 
