106 A Sketch of Comparative Embryology. [Februarý, 
single nucleus divides to form a compound body in which there 
is one large element with one kind of nucleus and numerous 
small elements, all with nuclei similar among themselves, but dif- 
ferent from the single larger nucleus. The same thing occurs 
when the egg sensu stricto, or the thelyblast, is developed. In the 
case of the egg, it is the larger element which is preserved as the 
female part; in the case of the spermatocyst, it is the smaller 
elements which are preserved as the male parts. The two pro- 
cesses are complementary. 
These facts have led to the following hypothesis of the relation 
of cells to the sexual elements. In an ordinary cell the two 
elements are intimately united in a latent condition, so that an 
ordinary cell is hermaphrodite or neuter, sexless, by which I mean 
it has no sexual differentiation. Diagrammatically this condition 
may be represented by Fig. 9, A. To form an egg the male por- 
tion is removed in several parts, which are the polar globules, 
while one large portion becomes the egg or thelyblast, Fig. 9, 2. 
To form the spermatozoa, the two elements separate, the mother 
nucleus, or female part, remains behind, and if my hypothesis is 
correct, it, as well as the egg, must be called a thelyblast; the- 
spermatozoa are discharged, and are capable of further vitality. 
FE F S 
They are the homologues of the polar globules. For both struc- 
tures the common name arsenoblast has been suggested. If the 
above hypothesis is valid, 
M 
l 
A 
5 ON then there is- a: fundá- i 
@® mental distinction between : 
@ @® cells on the one hand, and : 
BC @°¢ the genoblasts (the sexual | 
—Diagrams to show the relation a T products) on the other- — | 
Fic. 9. 
sexual products to cells. an ordinary c 
egg mii rw globules; G spermatocyst with every genoblast contains | 
spermat 
only one sexual element, 
every cell contains both. When sexual reproduction occurs, a — 
thelyblast from one source unites with an arsenoblast from 
another source—the two by their fusion complete a perfect cell, 
which is called the impregnated ovum. In the next article this : 
process will be described. 
In conclusion I wish to repeat that the conception of sex here 4 
advanced is only an hypothesis, which further research may cast 
aside, but which I hope may be confirmed, because it is already 
possible to bring forward many strong arguments in its favor. 
