No. 2.] DEVELOPMENT OF THE HUMAN COELOM. 399 
DEVELOPMENT OF THE MONKEY. (FROM SELENKA.) 
DIAMETER OF 
DIAMETER OF RTERTONIC 
Ovens VESICLE. 
Semnoplthecussmaurus, ~~) 312 = 1. i. s I.5 mm. -3 mm.1 
Semnopithecus pruinosus ....... copy 35 
@ercocebusjcynomolgus) 5+. 5. 2 igo ay et 
@ereocebusicynomolgus, 2 2 8 os 3. ss Osman Ziq kes 



The pictures Selenka gives indicate that the development of a monkey’s 
ovum is identical with that of the human ovum. At any rate, the few specimens 
Selenka publishes give results which are equal to the great number of specimens 
of human ova which have been published. This only indicates that many of the 
interesting problems relating to early human development will probably be solved 
by the study of the monkey’s ovum. There is but little doubt now that young 
monkeys’ ova will soon be obtained for study. 
MATERIAL EMPLOYED. 
During the last few years I have obtained a number of young 
human embryos from physicians in different portions of the 
United States, and to them I am under all obligation for the 
present study as well as for some others which are to follow. 
Nearly all of the specimens which I give in a table are well 
preserved, and a number of them are preserved excellently. 
All of the specimens were stained in alum carmine, and with 
the exception of Nos. XVII, XLIII, and LVII were cut trans- 
versely. These three were cut in sagittal sections. 
All of the specimens were hardened in alcohol, the value of 
which method I have repeatedly emphasized to my friends, and 
do continue to emphasize to those who may preserve specimens 
for my use in the future.? 
1 Not an embryonic vesicle, but only a disc. 
2 Neurenteric canal present. 
8 Embryologists usually recommend that human embryos should be hardened 
by placing them in dilute alcohol and then gradually increasing the strength of the 
alcohol. It has been my experience that by this treatment the specimen is injured 
by maceration due to the weak alcohol. A few years ago I emphasized the fact 
that the whole ovum should be placed in a large quantity of strong alcohol as soon 
as possible. It should be handled as little as possible before hardening it, thus 
preventing mechanical injury. By leaving the ovum closed the alcohol must first 
penetrate the chorionic and amniotic fluids before it reaches the embryo, and thus, 
