GERM GLANDS AND GERM CELLS OP FROG LARVAE 549 



were each day fed algae, the tadpoles of the other groups re- 

 ceived no food of any kind. 



The growth of both control and starved larvae ran parallel in 

 regard to size, for about six days, i.e., until April 16. 2 The in- 

 crease in size of the unfed tadpoles was probably due to the con- 

 sumption, of the surplus yolk material held in reserve within the 

 body cells. From April 16 on, however, the algae-fed tadpoles 

 increased rapidly in size, as compared to the starved animals, 

 and by April 27 were twice the size of the unfed larvae. 



On May 6, ten tadpoles of both the control and starved cul- 

 tures were killed and preserved for microscopic examination of 

 the gonads, by fixation in Flemming's solution. 



The control animals at this time measured 32 mm. in length, 

 whereas the starved tadpoles averaged but 12 mm. thus showing 

 a length difference of 20 mm. between the animals of the two 

 series. The controls revealed indications of limb development; 

 the limb buds of the hind legs were clearly discernible as 

 small, fleshy projections, just anterior and lateral to the anal 

 opening. A careful examination with the microscope failed to 

 show any indications of limb development among the starved 

 larvae. 



The gonads of the two series of tadpoles were sectioned at a 

 thickness of 7.5 p.. Heidenhain's iron hematoxylin stain was 

 used exclusively. A counterstain of congo red was also em- 

 ployed, but equally satisfactory results were obtained without 

 employing counter stains, especially in the young larvae. 



Microscopic examination of the germ gland anlagen and germ 

 cells of the two series of animals showed that the gross differ- 

 ences in size and somatic development, between fed and unfed 

 larvae, did not extend to size or developmental differences in the 

 germ cells. The germ cells of both control and starved animals 

 were of the primitive, sexually undifferentiated type. A more 

 rapid rate of cell division had evidently occurred in the algae- 

 fed larvae, for the number of primordial germ cells in the gland 

 was several times the number observed in the unfed larvae. 

 The nuclear structure of the sex cells of the two series appeared 



2 This experiment started in spring of 1915; completion spring of 1916. 



