Psychology. 743 
is important to emphasize : these movements do not appear to be 
directly provoked by an exterior object, as those of micro-organisms 
are ; the spermatozooid endeavors to reach an ovule which is frequently 
situated a great distance away ; this is the case particularly with 
animals that fecundate internally, — with birds and mammifers. A 
fact that is important to mention in a general way is the length of 
road the spermatozooid has to traverse before coming up with the ovule. 
" Let us now follow the spermatozooid in its journey to the ovule. 
extremely long. Thus in the hen the oviduct measures 60 centi- 
meters, and in large mammifers the passages have a length of from 25 
to 30 centimeters. We might ask ourselves how such frail and minute 
creatures come by a power of locomotion great enough to enable them 
to traverse so long a path. But observation discloses the fact that 
they are able to overcome obstacles quite out of proportion to their 
' size. Henle has seen spermatozooids carry along with them masses of 
crystals ten times larger than themselves, without appreciably lessening 
their speed. F. A. Pouchet has seen them carry bunches of from 
eight to ten blood-globules. M. Balbiani has attested the same fact. 
These globules, which have fastened themselves about the head of the 
spermatozooid, have each of them a volume double that of the head. 
Now, according to Welcker, the weight of a globule of human blood 
is 0.00008 of a miligramme : allowing that the spermatozooid has the 
same weight, we may then say that it is able to carry burdens four or 
five times heavier than itself." 
EXPLANATION OF PLATE. 
