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Wm. JS. Marsiiall, 



of all the niiclei would be about 0,0063 mm, not iiiiicli larger tliaii 

 those of the youngest embryo. 



Larva. In the youngest larvae the gonads are similar to what 

 we foimd in the oldest embryo, the structure of the nuclei is the 

 same, and no cell boundaries have as yet appeared. In a larva 

 2,1 mm long, we find that the three ovarian tubules have been 

 partially developed; each tubule has a widtb of 0.035 mm, making 

 the reproduetive organ larger than in the embryo, where we found 

 the entire gonad, but slightly larger than one of the tubules in this 

 larva. A view of an ovarian tubule from an larva 2,6 mm long 

 (Fig. 3), shows that the greatest change noticeable, is the appearance 

 of the cells; a small amount of cytoplasm around many of the nuclei 

 being marked off by a cell boundary, and this cytoplasm is darker 

 than that which is not so enclosed. Wheter or not all the nuclei 

 lie in cells, is difficult to determine, but this is the condition by 

 slightly older ones. The nuclei, 0,005 to 0,006 mm in diameter, 

 found in the gonads of this larva, are still similar in structure (Fig. 4) 

 to those of the embryo. In larvae of this age a very few mitotic 

 figures were seen, but these were not abundant. In looking over 

 sections of a few larvae, of this and of a slightly greater length, 

 we would find but two or three dividing cells in an entire gonad and 

 all seen were in the equatorial plate stage (Fig. 5). 



Ovary A. In larvae somewhat larger than this last one it is 

 easy to distinguish betweeu ovaries and testes, either by dissectiou. 

 or by a microscopic examination. Düring the early growth of the 

 larva, we find that but slight chauges take place in the structure of 

 the nuclei or of the ovary, the nuclei have increased a little in size, 

 but a greater change has taken place in the growth of the ovary 

 itself. In a larva 7 mm long sexual differentiation has become very 

 marked; the ovarian tubules are each 0,275 mm long, but they as 

 yet; show none of the parts which can so easily be distinguished in 

 older stages. The tubules are filled with a mass of cells which show 

 a greater difference in size and shape, than in structure. In each 

 tubule one can easily distinguish between a distal half, in which the 

 nuclei of the cells are small and ovoid, and a proximal half, containing 

 fewer cells but nearly all with larger nuclei. Grünberg (12) noticed 

 in Lepidoptera that at an early stage the oogonia all had their 

 Position in the distal, and the epithelial nuclei in the proximal, part 



