254 



PSYCHE. 



[April 189a. 



pleural thickenings of the second ab- 

 dominal segment are also more pro- 

 nounced than those of the succeeding 

 segments but much smaller than the 

 first pair. I could not make out that 

 they gave rise to oenocytes. As I had 

 no material of the later stages I was 

 prevented from following the develop- 

 ment of these organs further. It is pos- 

 sible that there are in the adult several 

 pairs of oenocyte clusters as in other 

 insects and that they develop from be- 

 fore backwards so that the stage which 

 I studied may have shown only the 

 formation of the first pair of anlagen. 

 It seems to me more probable, how- 

 ever, that Zaitha develops only one 

 pair of clusters and that the others have 

 atrophied to such an extent as no longer 

 to appear during ontogeny. 



Neuroptera. In the just-hatched 

 larvae of Sialis infumata a few oeno- 

 cytes were found as large clear cells 

 sticking in the pleural hypodermis be- 

 tween the insertions of the tergo-sternal 

 muscles. 



Trichoptera. Specimens of the 

 larvae of an unidentified Phryganeid 

 were torn open in normal salt-solution 

 and examined fresh or after treatment 

 with methyl-green osmo-acetic mix- 

 ture. In fresh preparations the gigantic 

 oenocytes (Fig. 1.) are yellow, more or 

 less rounded, and often provided with 

 delicate processes which are attached to 

 the tracheal hypodermis. The cyto- 

 plasm is usually finely granular ; the 

 chromatic skein of the nucleus is dis- 

 tinctly discernible in the unstained cell. 

 Methyl green stains both cytoplasm and 



nucleus deeply and of about the same 

 hue. This reagent, of course, accentu- 

 ates the chromatic skein. There are no 

 nucleoli. 



In some of the larvae all the oeno- 

 cytes contain vacuoles. These are ar- 

 ranged in a broad band surrounding the 

 nucleus midway between the nuclear 

 and cytoplasmic walls. These vacuoles 

 are but slightly refractive and are not 

 fat-globules. This condition of the 

 oenocytes was found in a number of 

 larvae and, I believe, represents a nor- 

 mal physiological state. Wielowiejski 

 has made a similar observation. One is 

 reminded of certain gland-cells which 

 store up vacuoles of a specific substance 

 in their cytoplasm, preparatory to se- 

 cretion. 



One of the facts brought out by 

 measurements of Xiphidium, viz : the 

 gradual growth of the oenocytes with 

 the growth of the insect, was again 

 clearly shown in the larvae of this 

 Phryganeid. Different stages gave the 

 following measurements. 



Cytoplasm. Nik lens. 



1. Larva just hatched, 12.0 |x 4.6 p 



2. Larva 13 mm. long, 40.S |x 15.6 (*. 



3. Larva 17 mm. long, 62.8 |a 20.3 p. 



4. Larva 25 mm. long, 103.7(1 29 5 u. 



c. Larva 30 mm. long, \ iV > < 5 > 



3 J ° I 166. 8 |a J ( 74. ji J 



Here the cytoplasm increases from 

 1 2. - 166.8 n, while the nucleus grows 

 from 4.6 - 74 n, so that the latter 

 undergoes a slightly greater relative 

 increase in size. In Xiphidium we 

 found the converse to hold good. 



Coleoptera. The oenocytes of 

 Photuris pennsylvanica (imago) are 



