454 



by small groups of closely packed, rather large cells (fig. 92) ; 

 they still lie quite close to the integument, and though they 

 occur elsewhere, are best seen at the posterior end of the larva. 

 They do' not occur in the head. 



In the larva of the first instar they can be seen (fig. 175) 

 as a small cluster of rounded cells, which have just grown 

 down into the body cavity from the ectoderm of the integu- 

 ment. The cells measure about 10/x in diameter, the nuclei 

 5J/A. They have a large karyosome, but the chromatin is not 

 markedly scattered through the nucleus. 



During larval life they grow downwards and increase 

 in size, attaining in the defaecating larva a diameter of 15/x, 

 while the nuclear diameter has increased to 8/x; a small 

 (plastin) nucleolus has begun to appear. The cytoplasm is 

 homogeneous. I could not observe any increase in the wwrnher 

 of the oenocytes, however. 



But as the larval oenocytes gradually disappear these 

 imaginal oenocytes replace them; they grow quickly in size, 

 and leaving the sites of formation migrate, by amoeboid 

 movement apparently, into the fat-body, among whose cells 

 they scatter themselves. They do not grow as large as those 

 of the larva (fig. 179), seldom exceeding 21fx in diameter, 

 with a nucleus of 9ya. The latter may be granular and may 

 show several small karyosomes. Occasionally in the four-day 

 pupa they may actually contain a gigantic nucleolus, contain- 

 ing minute crystals ; whether this is an indication of degenera- 

 tion I cannot say. 



It is important to note that the oenocytes are more 

 prominent in the larva than in the adult insect. This agrees 

 well with the view above expressed that their function is to 

 break down the storage products of the fat cells, as the 

 organism needs them, feeding being ever so much more active 

 during larval life. 



The Lateral Intestinal Glands. 



On either side of the intestine, just below the paired 

 hepatic caeca, are to be seen, in the mature larva, two 

 organs, whose existence has not, so far as I am aware, hitherto 

 been observed in insects. The organs are in the form each 

 of a long chain of very large, elongated cells about 60/x in^ 

 length, and presenting a weakly fibrous cytoplasm. Within 

 this delicate cytoplasm is a great heavily granular mass, oval 

 in shape, and about 55/x in length. It seems impossible that 

 it should be anything but a greatly hypertrophied nucleus 

 (fig. 169). A nucleolus may be present. 



In the larva of the first instar th^s^ organ- is. indistinctiy 

 seen as a number of faintly fibrous cells just below the hepatic 



