422 EDWARD E. WILDMAN 
within the male. At the suggestion of Prof. T. H. Montgomery, 
Jr., I undertook this study. I wish here to express my deep 
appreciation of Professor Montgomery’s kindly interest in my 
work, and of his helpful advice and criticism, during the course 
of the observations. I very much regret that this report was 
not finished in time to be reviewed by him, for this is a field of 
research in which Professor Montgomery stood preéminent. 
THE REFRACTIVE BODY 
Place and manner of its formation 
Notwithstanding the fact that the spermatogenesis of the nem- 
atodes has been studied since 1858, the history of the refractive 
body had remained unknown. During this time the study of 
no animal has contributed more to our knowledge of the cytology 
of the germ cells than that of the common nematode parasite of 
the ,horse, A. megalocephala. The brilliant researches of Van 
Beneden, Hertwig, Brauer, Tretjakoff and others leave little to 
be desired concerning the nuclear phenomena during spermatogen- 
esis. The laws of nuclear structure and behavior here discov- 
ered have been found to be of very general application. But 
the observations of these authors on cytoplasmic structures, 
accurate and extensive as they are, lack the completeness of a 
final interpretation, because none of them saw the last stage in 
the process of sperm development. 
Throughout the incomparable researches of Van Beneden on 
the development of the Ascaris spermatozoon there is no indi- 
cation that he even suspected the formation of the refractive 
body within the vas deferens. His excellent figures represent the 
various stages of its development as entirely within the uterus. 
He believed that the paternal element left the male in the form 
of the spermatid, spherical or slightly conical in form but with 
no trace of the refractive body. 
At the proximal end of the uterus one always finds a great 
number of spermatozoa crowded among the eggs and uterine 
epithelial cells. This region Van Beneden named the ‘receptac- 
ulum seminis.’ Among this crowd of spermatozoa are to be 
