2 Psyche [February 
studied the spermatogenesis of Samia cecropia L. Spermatogonia 
or young spermatocytes were kept alive for about three weeks, and 
the follicle membrane for some weeks more. This piece of work 
and that of Lewis and Robertson, 1916, on the male germ cells of 
Chorthippus curtipennis Scudd (Stenobothrus curtipennis Harris) 
seem to be the only examples of insect tissue cultivation found in the 
literature. 
For the experiments here described the larvee of Malacosoma 
americanum, Cirphis unipuncta, Laphygma frugiperda and Porthetria 
dispar were used. My method did not differ materially from those 
of Harrison, Carrel, Goldschmidt, ete. However, since most of 
my experiments dealt with the cultivation of insect blood I will 
briefly outline the method of procedure. The larvee to be operated 
upon are held upside down in one hand and the anterior and 
posterior halves bent back.* A proleg is then thoroughly washed 
with 80 to 95 per cent. alcohol after which it is clipped with very 
fine aseptic scissors. The drop of blood which oozes out is caught 
on a sterile cover slip which is then placed on a sterile depression 
slide and the edges sealed up with sterile vaseline. A great many 
slides were prepared in this manner, 2.e., the blood corpuscles were 
simply mounted in their own plasma. In other cases Locke’s 
solution,' or a mixture of Locke’s solution and plasma was found 
satisfactory. In general Locke’s solution is isotonic with insect 
tissue and can be very freely used for cultivation and for the wash- 
ing out of old cultures in order to free them of harmful by-prod- 
ucts. Locke’s solution has no particular advantage over the 
plasma, except that the preparations are a bit more transparent, 
owing to the fact that large amounts of fibrin have been eliminated. 
Blood was obtained from healthy Malacosoma americanum 
larvee and six slides prepared. In a few days some of the blood 
cells disintegrated, but the majority lived and multiplied. In ten 
days beautiful syncytia had formed (PI. I, fig. 1). At the end 
of this time three of the slides were inoculated with some polyhedral 
material which had been passed through Berkefeld Grade “N” 
candles. The other three slides were kept as checks. All slides 
were observed for forty days. After this the cells in both experi- 
ments and checks ceased growing and disintegrated normally. 
1 Locke’s solution consists of NaCl 0.9 per cent., CaClz 0.025 per cent., KCl 0.042 per cent., 
NaHC0Os 0.02 per cent., Dextrose 0.25 per cent., Peptone 0.2 per cent. 
