HUMAN TESTIS AND EPIDIDYMIS 409 



one of which joined with the rete. But anastomoses among the 

 vasa efferentia of man must be considered as of rare occurrence. 

 Convolutions of the vasa efferentia and the ductus epididymis 

 Dogin to appear at about the fourth month of fetal life, as was 

 found to be the case with the testis tubules. Here also the convo- 

 lutions are in short, stiff curves, and here also certain portions of 

 the tubules form groups of coils, joined by unconvoluted portions, 

 each group ultimately developing a vascular unit of its own. In 

 the case of the coni vasculosi, single vasa efferentia are usually 

 separated by connective tissue, though occasionally two or more 

 may be intertwined; each conus contains several units. In posi- 

 tion the coni are of two distinct groups, lying mesial and lateral 

 respectively to the convolutions of the ductus epididymis. This 

 arrangement, not describea in the text-books, seems to be due 

 to the two sets of mesonephric tubules which enter the duct on its 

 ventral and dorsal aspect respectively, as described above; the 

 ventral tubules form the lateral group of coni vasculosi. The 

 head of the epididymis thus shows three main lobes, more or less 

 distinct, the middle lobe containing the ductus epididymis. 



CONCLUSIONS 



1. The testis cords, growing from the germinal epithelium of the 

 genital ridge, form a network with three sets of anastomosing 

 branches. After completion, this network breaks down partially, 

 leaving certain cords as persistent stems. The tubules of the 

 adult show, in their course, connection, and position in the testis, 

 traces of this network. Testis tubules may be single, ending 

 blindly, may branch, or may anastomose. 



2. The unit of the testis is a considerable number of coils of one 

 tubule, enclosed within a sheath; there are many units for each 

 tubule, connected by less convoluted portions. 



3. The spermatic artery is not a special vessel, as in the pig, 

 etc., but the survivor of the mesonephric arteries in the genital 

 region. The others were obliterated by stretching and by the 



THE AMERICAN JOURNAL OP ANATOMY, VOL. 11 , NO. 4. 



