594 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
cular cells and the true ova. The former, in origin, structure, and 
function, are apparently the equivalents of the follicular cells of the 
testis. A point of some interest is the relation of these cells to the 
cells of Sertoli in mammals. The author believes that they are the 
homologues of the cells of Sertoli, but they present many differences 
from the conditions described by several authors for the latter. Thus 
they are not interstitial cells as some suppose Sertoli’s cells to be ; 
they do not give rise to spermatogonia; they are not the residue of 
cells which have given rise to spermatozoa ; they are not products of 
degeneration ; they do not form a syncytium (cf. Regaud, supra , p. 575) ; 
all of which assertions have been made by different authors for the cells of 
Sertoli. In brief, the follicular cells of insects are hypertrophied primi- 
tive spermatic cells, which ultimately break up to feed the spermatozoa. 
Post-embryonic Development of Entomophagous Hymenoptera * — 
L. G. Seurat has made an elaborate series of investigations on this 
subject with special reference to the Braconidae. The observations have 
in large part been made on Doryctes gallicus Rh., whose larvae are exter- 
nal parasites of the larvae of longicorn beetles. The paper is divided 
into three parts. Of these the first contains an account of the anatomy 
of the adult Doryctes gallicus and a description of the phenomena of the 
brief adult life (mating, egg-laying). In the second part the general 
phenomena of larval life in the Braconidae, Ichneumonidae, and Cbalei- 
didae are described and compared, while the third part is devoted to a 
detailed study of the larval life of Doryctes gallicus. The following are 
the more general conclusions deduced by the author from his investiga- 
tions. He agrees with Rheinhard and Janet in finding that the thorax 
of the Hymenoptera consists of four segments, and bears three pairs of 
stigmata. The number and distribution of the stigmata of the abdomen 
vary not only in different families, but within the limits of a single 
family. In the female Doryctes the gut and the Malpighian tubules are 
greatly reduced, the condition of the former rendering food-taking in 
adult life impossible. The ovaries, on the other baud, display a high 
degree of development, all the eggs being mature at the same time. The 
genital armature arises from the two penultimate segments of the abdo- 
men. As to the larvae, the simplest case is where these are external 
parasites. They then suck the tissues of the host through a small 
aperture in the latter’s skin. The stomach is enormously enlarged, and 
does not communicate with the rectum until after the formation of the 
cocoon at the end of larval life. In larvae which are internal parasites, 
the alimentary canal is similar to that of the external forms, but the 
tracheal system is closed and respiration takes place through the skim 
The larvae can move about within the host, and are possessed of a special 
locomotor organ whose significance has hitherto not been recognised. 
The tracheal systems of different larvae show marked differences which 
are of considerable systematic importance. 
Life-history of Trama radicis.j — S. Del Guercio gives an account 
of this root-aphis, describing the parthenogenetic form which begins the 
cycle, the winged forms which migiate from one plant to another, and. 
* Arm. Sci. Nat., x. (1899) pp. 1-159 (5 pis. and 16 figs.). 
f Bull. Soc. Entomol. Ital., xxx. (1899) pp. 187-98 (6 figs.). 
