[February 1892. 



PSYCHE. 



217 



portant tissue, so intimately concerned 

 with the nutrition of the organs. Of 

 these attempts two, however, are wor- 

 thy of special attention — one by Wie- 

 lowiejski, 1 who approaches the subject 

 from the anatomical side, and another 

 by Graber, 2 who contributes some valu- 

 able observations of an embryological 

 nature. 



Wielowiejski includes under the term 

 blutgewebe (blood-tissue) the follow- 

 ing structures: 



1. The blood corpuscles; 



2. the fat-body proper ; 



3. the pericardial fat-body ; 



4. the oenocytes, of which he 



distinguishes three varieties in 

 some insects. 

 To this list I would add : 



5. The garland-shaped cord of 



Muscid larvae ; and 



6. a peculiar organ, which I may 



call the suboesophageal body, 

 and which I have found in the 

 embryos and young larvae of 

 Blatta and Xiphidium. 

 Wielo\Aejski is careful not to main- 

 tain a common origin for all the com- 

 ponents of his "blutgewebe" but 

 comprises them under a common head- 

 ing on purely physiological grounds, as 

 he expressly states. They are blood- 

 tissue to the extent u dass sie alle von 

 dem sie umgebenden medium gewisse 

 stoffe aufnehmen, zeitweise aufspeich- 



1 Ueber das blutgewebe der insecten. Z eitsc hr. f. 

 wiss. zool., 43. bd. p. 512-536. iS86. 



2 Ueber die embryonale anlage des blut- und fett- 

 gewebes der insekten. Biol, centralbl., ;ii bd. nos. 



7 u. S. p. 212-224. 1S91. 



era resp. verarbeiten und irgend 

 welche umsatzprodukte an dasselbe 

 zuriickgeben und dadurch auf die in 

 den hauptgeweben des organismus 

 vor sich gehenden assimilations und 

 desassimilationsprocesse einen einfluss 

 ausiiben." 



Graber is less cautious and does not 

 hesitate to conclude that the different 

 tissues constituting Wielowiejski's blut- 

 gewebe are genetically related. Stated 

 very briefly these are the conclusions at 

 which he arrives. 



1. The oenocytes are derived 



from the ectoderm ; 



2. They are metamorphosed into 



the fat-body ; 



3. The blood-corpuscles arise 



from the fat-body (and also 

 from the oenocytes?). 



Ergo the fat-body and the blood are 

 ectodermal structures ! Certainly a re- 

 markable conclusion and one which an 

 even more intrepid investigator might 

 hesitate to advance in these days when 

 we are so accustomed to derive the 

 blood-corpuscles and connective tissue 

 from the middle germ-layer. While 

 my own conclusions differ radically 

 from Graber's, so far as the origin of 

 the fat-body is concerned, I cheerfully 

 confess that his interesting paper was 

 the means of calling my attention to this 

 much neglected subject. 



Even the earlier entomotomists were 

 familiar with certain huge cells associ- 

 ated with the fat-body. By some they 

 were supposed to assist in respiration 

 since they were often found attached to 

 the fine tracheal ramifications. Graber 



