INTERSTITIAL CELLS OF URODELE TESTIS 265 



the cells possess noticeable polarity (nucleus toward one end, 

 enlarged centrosphere, granules, etc., toward the other, in Nec- 

 turus), they show no particular orientation of the cell body with 

 respect to either lobule or blood vessel. 



The inconstancy of the interstitial cells in urodeles would fur- 

 ther tend to preclude their recognition as a gland in the morpho- 

 logic sense of the term. Lacking for several weeks in Necturus 

 and Diemyctylus, and probably for several months in Gyrinophi- 

 lus, Plethodon, and Spelerpes, they persist in Desmognathus 

 until those of the succeeding year develop, and hence in the 

 mature male are, as a rule, never absent. In any event, in the 

 animals in which they appear, the individual cell is of transitory 

 character — a mere temporary modification of a stromal cell. The 

 absence of the cells from the sexually immature animals I have 

 studied is further evidence of their lack of individuality as a 

 cell type. 



If the cells subserve the purpose of elaborating an internal 

 secretion of specific action, that is, if they constitute a gland in 

 the physiologic sense, their absence from the sexually immature, 

 and temporary absences from the adult, seem anomalous, to say 

 the least. 



A constant relation of their development to phases of the sex 

 cycle (other than to lobule degeneration, in which relation all 

 urodeles agree) seems difficult to ascertain, as in many urodeles 

 so little of the life-history and mating habits is known. It would 

 appear that in Necturus and Cryptobranchus, and perhaps in 

 Diemyctylus as well, the late summer or fall matings occur at a 

 time when interstitial cells have been absent for several weeks, 

 and too soon after the emptying of the lobules for the new inter- 

 stitial cells to have reached any conceivable state of secretory 

 activity. A spring mating in Necturus, if it should occur, would 

 take place when the cells were at or somewhat past their maxi- 

 mum; the spring mating of the one Amblystoma male I have 

 examined must have occurred toward the later part of their 

 cycle. That interstitial cells in each of these cases regulate the 

 appearance of secondary sex characters, as well as the instincts 

 of the mating season, can hardly be given credence. 



