OF MICRO-ORGANISMS. 79 



with animals that fecundate internally, with birds and 

 mammifers. The place of fecundation is still imper- 

 fectly known. Coste at one time accepted the theory 

 that the spermatozoid and ovule met in the ovary. 

 Fecundation probably takes place in the fore part of 

 the oviduct. It has little to do with our purpose, how- 

 ever, to solve this delicate question precisely. A fact 

 that is important to mention in a general way is the 

 length of road the spermatozoid has to traverse before 

 coming up with the ovule. 



Let us now follow the spermatozoid in its journey 

 to the ovule. It is known that the road it has to tra- 

 verse is, in certain instances, extremely long. Thus, 

 in the hen the oviduct measures 60 centimeters, 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 spermato- 

 zoids carry along with them masses of crystals ten 

 times larger than themselves, without appreciably les- 

 sening 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 

 spermatozoid^ have each a volume double that of the 

 head. Now, according to Welcker, the weight of a 

 globule of human blood is 0.00008 of a milligramme: 

 allowing that the spermatozoid has the same weight, 

 we may then say that it is able to carry burdens four 

 or five times heavier thanatself. 



The length of road traversed is not the only remark- 



