CHAPTER V 



SPERM ATOGENESIS INSEMINATION 



" Denique per maria ac mentis fluviosque rapacis 

 Frondiferasque domos avium camposque virentis, 

 Omnibus incutieus blandum per pectora amorem 

 Efficis ut cupide generatim ssecla propagent." 



LUCRETIUS. 



THE spermatozoa, or reproductive cells of the male, were ob- 

 served as far back as the year 1677, when Hamm, who was a 

 pupil of Leeuwenhoek, directed the latter 's attention to them. 

 Leeuwenhoek, however, did not understand the significance of 

 what he saw. 



Spallanzani l was the first to show that the presence of 

 spermatozoa in the semen was an essential factor in fertilisation, 

 since the filtered fluid was found to be impotent. Subsequently 

 Kolliker 2 discovered that the sperms arise from the cells of the 

 testis, and Barry 3 observed the conjugation of sperm and ovum 

 in the rabbit. 



Van Beneden's discovery that the nuclei of the conjugat- 

 ing cells both ova and spermatozoa contain only half the 

 number of chromosomes that they had originally has been 

 referred to in the preceding chapter, where the maturation 

 phenomena in the ovum have been briefly outlined 4 (p. 130). 

 The four products of division formed at the completion of re- 

 duction in the male differ from those in the female in that each 

 of them is a functional conjugating cell. Before describing the 

 reduction process in detail it will be well to give a short account 

 of the structure of the testis. 6 



1 Spallanzani. Dissertations, English Translation, vol. ii., London, 1784. 

 a Kolliker, Bcitriiyc zur Kenntniss dcr Cfescklcchtsvcrhaltnisse, &c., Berlin, 1841. 



3 Barry (M.), " Spermatozoa observed within the MammiferousOvum,"/Vu7. 

 Trans., 1843. 



4 For accounts of the history of the chief discoveries relating to the 

 spermatozoa, fertilisation, &c., see Thomson, The Science of Life, London, 

 1899, and Geddes and Thomson, The Evolution of Sex, 2nd Edition, 

 London, 1901. 



5 See Barry (D. T.), " The Morphology of the Testis," Jour, of Anat. and 



Piiys., vol. xliv., 1910. 



165 



