388 TH. H. MONTGOMERY jr., 



It might be objected that in the largest nuclei, where the chro- 

 matin nucleolus is largest, the true nucleolus attached to it has 

 frequently still as great a size as in the smaller nuclei, i. e. that 

 there appears to tal^e place no gradual diminution in the mass of the 

 attached true nucleolus. But this objection does not hold good, for 

 as the nucleus increases in size not only does the chromatin nucleolus 

 and the chromatin increase in size and amount, but there is also an 

 increase in the amount of the true nucleolar substance: for each of 

 the largest nuclei frequently contains as many as three or four true 

 nucleoli, each of them fully as large or larger than a nucleolus of an 

 undifferentiated hypodermal cell. Accordingly, while the chromatin 

 nucleolus may be continually absorbing substance from a true nucleolus, 

 the latter may yet remain constant in size by the addition to it of 

 nucleolar substance from without. 



There are still points of great interest in regard to the signi- 

 ficance of the chromatin nucleolus, which remain to be determined. 

 Why is there always a single chromatin granule which undergoes such 

 metamorphosis? By what is it represented in the undifferentiated 

 hypodermal cell? Two possibilities suggest themselves: either there 

 is in each nucleus a particular true nucleolus which has the power 

 of producing peculiar changes in the chromatin granule with which it 

 happens to come in closest contact. Or, and perhaps more probably, 

 there may be in each nucleus a specialized chromatin granule destined 

 to undergo this metamorphosis; and if this represented the whole or 

 the part of a metamorphosed chromosome, the chromatin nucleolus 

 here might be comparable to that of insect spermatocytes. In insect 

 spermatocytes, the chromatin nucleolus and the true nucleolus may 

 be either separated (Euchisfus, Anasa) or they may be in contact 

 {Harpalus, Phymata). 



3. Hypodermal spîne-producîng Cells. 



At various points on the surface of the body, particularly laterally, 

 are found long cuticular spines sunk into the surface of the cuticle 

 (Fig. 7 Sp). Beneath each such spine the hypodermis is modified so 

 that in the place of the undifferentiated epithelium, or below it, is 

 found an enlarged cell syncytium, which projects slightly into the body 

 cavity (Figs. G, 7). In this cytoplasmic mass are a few nuclei of 

 different sizes, but each of them considerably larger than those of the 

 contiguous hypodermis. These cells are evidently the producers of 

 large spines. Their cytoplasm stains less intensely, but more uni- 



