64 R- R- HUMPHREY. 



modifies to some extent the end result. Hence one may expect a 

 certain variation in lobe number even in animals of exactly the 

 same age. 



So, too, on this basis, the occasional differences between the 

 testes of the individual male become understandable. Figures 22 

 and 23 illustrate the testes from animal number 437, killed on 

 June 26. One testis (Fig. 22) shows a well-developed anterior 

 lobe. In the other (Fig. 23) the disappearance of this lobe is 

 practically complete. Nevertheless the almost microscopic en- 

 largement containing degenerating lobules and interstitial cells 

 shows that a functional lobe occupied this region in the preceding 

 summer. At the caudal end of the testis represented in Fig. 23 a 

 small lobe is developing; in the other (Fig. 22) only a slender 

 caudal germ-cell cord appears. Clearly the one testis is a season 

 in advance of the other, as evidenced both by the earlier disap- 

 pearance of a lobe anteriorly and the earlier development of a new 

 lobe caudally. Whether in the animal's first year of sexual ma- 

 turity only one testis had become functional, or whether at some 

 time later the spermatogenetic processes were retarded in one 

 organ, it is impossible to state. Other animals have been found in 

 which the two testes differ only in the size of the anterior lobes, 

 they being of the types shown in Figs. 15 and 16. Still other 

 males show differences only in the stage of development of the 

 posterior lobes; animals are frequently found with one testis of 

 the type shown in Fig. 4, while the other is as well developed as 

 that in Fig. 5. Testes differing as do those of Figs. 5 and 6 have 

 also been removed from a single individual. All the differences 

 so far encountered, however, are but further evidence that the 

 multiple testis is an expression of the spermatogenetic processes. 

 Considering the lobes as structures of a segmental origin, or as 

 divisions of the testis associated merely with the body size, the 

 differences found in a single animal would be difficult of interpre- 

 tation ; realizing the manner in which lobes arise, run their course, 

 and disappear, the occurrence of such differences is even to be 

 expected. Though found in but a small number of the males 

 studied, such differences are by no means rare ; and, when found, 

 they are to be looked upon as a normal result of the different modi- 



