58 C. T. VORHIES. 



be due to the metabolic activity of the gland (Marshall and 

 Vorhies, 1906). 



On account of the difficulty of keeping the larvae in the lab- 

 oratory the exact ages of the larvae with reference to the follow- 

 ing events have not been obtained, but that is scarcely necessary 

 for the purpose of this work. With glands from larger and larger 

 larvae, more and more of the nuclei are found to contain two 

 nucleoles, occasionally three or four are present (Figs. 7, 8), and 

 in larvae about one week old, and 2 mm. or more in length 

 (which may have molted) as many as 4-7 nucleoles are typically 

 present in each nucleus (Figs. 8, 9). The nucleoles now in- 

 crease in number continuously as the nuclei increase in size 

 (Figs. 10-14), and, except that they become somewhat more 

 uneven in size and more irregular in shape, there is little to be 

 noted. A more detailed account with drawings showing their 

 characteristics in various large nuclei is contained in the 1906 

 paper already referred to. 



The changes in form of the nuclei, already briefly mentioned, 

 consist first in a lengthening in the direction of the circumference 

 of the gland (Figs. 2, 4-7); in a larva one week old, the nuclei 

 are two or three times as long as they are wide (Figs. 7-9). 

 It will be noted that there is a marked increase in number of 

 nucleoles before there is any great change in shape of the nuclei 

 (Figs. 9, 10). Swellings next appear, which elongate and develop 

 into branches (Fig. 11). Since there are no distinct centers of 

 branching (Vorhies, 1905), as figured by Henneguy (1904), 

 there is no regular order of development to be traced. At first, 

 it appears that a majority of the elongated nuclei have two branches 

 at one end forming a T-figure, or two at each end, forming a kind 

 of modified H-figure (Fig. 12), but if there really is any such 

 tendency the increasing complexity of the branch system soon 

 obscures it. The complexity simply increases with the increase 

 in size of the cell (Figs. 13, 14). There does not, however, ap- 

 pear to be a high degree of correlation between the size of the 

 cell and the space occupied within it by the nucleus (Marshall 

 and Vorhies, 1906, Figs. 1-6). 



The condition of the chromatin remains the same, so far as its 

 staining reaction and appearance are concerned, throughout the 



