116 
J. T. CUNNINGHAM. 
tended with ova, the spermatozoa would be carried down by the 
descent of these if they were not protected in the deep furrows 
and depressions of the uterine epithelium. A large number in 
excess of those which effect an entrance into ova are carried 
down mechanically, but as these unattached spermatazoa 
diminish in number towards the lower end of the uterus, they 
probably pass up again along the epithelium by means of their 
amoeboid movements. 
Structure of Spermatozoon. — The ripe spermatozoon 
consists of two parts : 
(1) A head of hemispherical shape enclosing a nucleus com- 
posed of chromatin only. Round the nucleus is a perinuclear 
layer finely punctated and with no distinct boundary, and 
external to this is a cortical layer composed of a reticulum of 
moniliform threads. 
(2) A tail which may have one of various shapes. The tail 
is enveloped by a membrane which ends in a free border where 
the head and tail join, the head being destitute of membrane. 
The substance of the tail is iu the young state entirely proto- 
plasmic, but in older spermatozoa contains a refringent body of 
larger or smaller size ; a layer of protoplasm persists between 
the membrane and the refringent body. 
The structure of the protoplasm of the head is easily seen, 
and the author takes occasion to point out that, according to 
researches of his own, the fibril of a striated muscular fibre 
has a structure similar to that of the moniliform fibrils of this 
protoplasm. He thinks it probable that such a structure is 
common to all protoplasm. 
The spermatozoa when first introduced into the female 
organs are spherical in shape and completely destitute of 
refringent body. One half of the sphere is covered by a layer 
of substance in the form of a cup which is more homogeneous 
than the rest of the sphere. This cup grows out into the form 
of a papilla, and increasing in size gives rise to the tail. The 
first stage of its growth gives the spermatozoon a pyriform 
shape; then by farther elongation of the tail the whole appears 
like a bell suspended by a string ; this is the campanuliform 
