April 1S92.] 



PSYCHE. 



255 



of huge dimensions like those of the 

 Trichopteran described above ; their cy- 

 toplasm measuring 1 1 S. 5 — 1 S5 . n across, 

 while their nuclei range from 33.5 — 

 60. I*. The cells are disposed in loose 

 clusters in the pleural region of the ab- 

 domen and resemble their homologues 

 in European Lampyrids. 



In some Malacodermata Wielowiejski 

 distinguished three different varieties of 

 oenocytes according to size. In the 

 Lampyrids he found only those of me- 

 dium size — corresponding to the sec- 

 ond variety of other Malacodermata, and 

 suggests that in the fire-flies the "kleine 

 oenocyten" (third variety) may be 

 converted into the photogenetic organ. 

 It is clear that if the "kleine oenocy- 

 ten" are true oenocytes and if, more- 

 over, Wielowiejski's suggestion is well 

 founded, the photogenetic organs of the 

 Lampyridae must be ectodermal struct- 

 ures. If on the other hand these inter- 

 esting structures originate from the fat- 

 body, as is usually maintained, they 

 must be mesodermal. 



In Photuris pennsylvanica the two 

 layers of the light-organ consist of cells 

 which closely resemble the elements of 

 the fat-body proper. The cells consti- 

 tuting the inner layer have the same size 

 and much the same appearance ; their 

 nuclei do not differ from those of the 

 fat-body ; in the outer layer, which is 

 more especially concerned with the 

 photogenetic function, the cytoplasm is, 

 of course, considerably altered, but the 

 nuclei are indistinguishable in every 

 particular from those of the fat-cells. 

 The resemblance between the fat-body 



and the light-organ is so great that I do 

 not doubt their genetic lelationship 

 though I have not studied the devel- 

 opment. 



Lepidoptera. Few insects appear 

 to be better adapted for tracing out the 

 origin of the oenocytes than the Lepi- 

 doptera. This is especially true of the 

 larger Bombycid moths. That the seg- 

 mental cell-clusters arise by delamina- 

 tion from the ectoderm was conclu- 

 sively made out in the embrvos of 

 Platysa?nia cecropia and Telea poly- 

 phemus. Each cluster is several cell- 

 layers in thickness and lies just behind 

 and a little ventrad to an abdominal 

 stigma. The succulent cells constituting 

 the cluster are at first polygonal from 

 mutual pressure, but as the time for 

 hatching approaches, they become 

 rounder and more loosely united. I 

 have not traced them through the larval 

 stages and merely record these frag- 

 mentary observations because they com- 

 pletely confirm Tichomiroff's and 

 Graber's observations on the origin of 

 the oenocytes from the ectoderm. 



Diptera. Oenocytes probably occur 

 throughout this order. To the families 

 in which they were found by Wielo- 

 wiejski (Chironomidae, Tipulidae, Culi- 

 cidae, Tabanidae, Syrphidae, Muscidae, 

 Pupipara) I would add two others 

 (Cecidomyidae and Simulidae). 



In the larvae of Cecidomyia anten- 

 nariae beautiful large oenocytes occur 

 in metameric clusters, each of which 

 consists of about five cells. These 

 seem not to be so regularly arranged as 

 the oenocytes of Chironomus (Wielo- 



