256 



PSYCHE. 



I April 1S92. 



wiejski) . One cell of each cluster is situ- 

 ated at some distance from the others 

 but dorsad and not cephalad as in Chir- 

 onomus. The cells measure 45.- 7$- v- 5 

 their nuclei 15. p.. They are round or 

 slightly oval, and flattened in the same 

 direction as the hypodermis, in niche- 

 like excavations of which they lie. 



In the young pupa they lose their 

 connection with the hypodermis, be- 

 come spheroidal and vacuolated and 

 their nuclei decrease in size. 1 have 

 failed to find any traces of oenocytes in 

 the mature pupa and imago. 



In the larva of Simulia the oenocytes 

 resemble those of Cecidomyia. 



The above insects belonging to many 

 of the natural orders were also studied 

 with a view to establishing the origin of 

 the blood-corpuscles but my results were 

 purely negative. I saw nothing to sup- 

 port Schaefler's view* that the corpus- 

 cles arise from the fat-body. Such an 

 origin is improbable ct priori inasmuch 

 as the cells composing the corpus ad- 

 iposum are specialized for storing up 

 fat and urates. That fat-globules and 

 urates in the blood-corpuscles do not 

 prove a genetic but only a physiological 

 relationship between the fat-body and 

 the blood is obvious if we stop to ask the 

 question : How do the fat and urate in- 

 clusions reach the fat-body ? It is most 

 natural to suppose that they are trans- 

 ported thither by the blood-corpuscles. 

 That the reverse may frequently be the 

 case, viz : that the blood-phagocytes may 



*Beitrage zur histologic der insekten. II. Ueber blut- 

 bildungsheerde bei insectenlarven. Sprengel's Zool. 

 Jahrb.,3 bd. heft 4. 1SS9. 



receive their fat-globules from the fat- 

 body and carry them to other parts of 

 the organism to be utilized in the meta- 

 bolic processes which are continually 

 taking place, is, I admit, quite as 

 probable. But neither of these pro- 

 cesses throws any light on the origin of 

 the blood-corpuscles themselves. 



In the embryo the blood-corpuscles 

 probably arise from undifferentiated 

 mesodermic tissue. They are often 

 found in different stages of caryokinesis 

 and I can see nothing improbable in the 

 supposition that they may continue to 

 multiply throughout postembryonic life. 

 It is also probable that mesodermic cell- 

 masses of an undifferentiated nature, 

 associated for obvious physiological 

 reasons with the fat-body, may function 

 as haematogenic centres during the 

 larval stages. For all his figures and 

 descriptions prove to the contrary, 

 Schaefler's "blutbildungsheerde" may 

 be such undifferentiated mesoderm- 

 masses and not portions of the true fat- 

 body at all. 



In this connection I may mention a 

 very interesting organ which I have re- 

 cently found in embryos of Blatta and 

 Xiphidium and which appears to have 

 some physiological connection with the 

 other members of the " blutgewebe." 

 This is a large v-shaped mass of cells 

 situated just beneath and attached to 

 the inner end of the oesophagus (stom- 

 odaeum) where the two entodermic 

 strands diverge. This cell mass lies 

 almost wholly in the trito-cerebral 

 (second antennary?) segment and, I be- 

 lieve, represents a modification of the 



