GERM GLANDS AND GERM CELLS OF FROG LARVAE 555 



account for the increase in growth of the tadpoles, for they re- 

 ceived no food of any kind. 



None of the starved animals revealed any indications of limb 

 buds. 



The control animals for this culture averaged in length 53 mm. 

 All of the larvae possessed well developed hind limbs. 



The structure of the germ cells and the germ glands of the fed 

 and unfed animals presented interesting contrasts when exam- 

 ined microscopically. The germ cells of the starved larvae re- 

 tained the primitive, undifferentiated character of primor- 

 dial germ cells with this exception — that they contained no yolk 

 granules. The size and average number of the cells in trans- 

 verse section had not increased any when compared with the 

 series killed ten days previous. No nuclear changes had oc- 

 curred; nor had sexual differentiation taken place (fig. 5). 



Contrasted with the germ cells of the starved cultures, those 

 of the controls were far along in the developmental cycle. All 

 of the germ cells were in synaptene or pre-synaptene stages in 

 the larvae of the female sex. The germ cells appeared slightly 

 larger than those of the unfed animals, but this is very likely due 

 to the onset of the growth period of the young oocytes which 

 occurs at the end of the synaptic stage. The average number 

 of germ cells visible in transverse sections was very large as com- 

 pared with the unfed animals of the same age (fig. 6) . 



June 7 another series of fed and unfed larvae was killed. 

 The starved animals were, at this time, very sluggish, swimming 

 about only when disturbed. The skin over the abdominal region 

 appeared transparent, and through it, the shriveled viscera were 

 plainly visible. The mortality among the starved larvae became 

 so great at this time that it was found necessary to feed the tad- 

 poles a few wisps of algae in order to prolong the experiment. 



The starved animals when killed measured 15 mm. and a 

 careful microscopic examination failed to reveal limb buds in any 

 of them. Contrasted with the unfed animals, the controls were 

 in advanced stages of metamorphosis. They averaged in length 

 60 mm., and had well developed fore and hind limbs. The tails 

 of a few of the controls appeared frayed and ragged along the 



