PSYCHE, 



CONCERNING THE "BLOOD-TISSUE" OF THE INSECTA.— III. 



BY WILLIAM MORTON WHEELER, WORCESTER, MASS. 



Rhynchota. As representative of 

 the Phytophthires the just-born young 

 of a wax-secreting Aphid, which in- 

 fests the alder, were studied. In sec- 

 tions the whole body-cavity was found 

 to be filled with a reticulate fat-body, 

 the nuclei of which measure only 3.5 |*. 

 The oenocytes are scattered here and 

 there throughout the reticulum appar- 

 ently without any definite arrangement. 

 They are large, brownish, opaque cells 

 with sharp contour. The cytoplasm 

 measures 1 2-1 8 k-; the nucleus 5- 

 55 H-. Thev seem to have no morpho- 

 logical connection with the fat-body but 

 to be merely slung in its meshes. The 

 nuclei stain deeply and present the typi- 

 cal finely wound chromatin skein. Some 

 of the scattered cells were found in the 

 three thoracic segments, whither they 

 had probably migrated during embry- 

 onic life from the pleural walls of the 

 abdomen. In the prothorax only two 

 oenocytes were found and these were 

 placed symmetrically one on either 

 side in the pleurae. 



In the mature embryo of Ranatra 

 fusca oenocvte-clusters occur in five of 

 the abdominal segments. They are 

 huge yellow cells with nuclei rich in 

 chromatin and are lodged in niche-like 

 depressions of the pleural hypodermis. 



My observations on the oenocytes of 

 Zaitha Jlitminea are limited to a stage 

 of the embryo immediately preceding 

 revolution. I find in the abdomen, just 

 outside the appendages and stigmata, a 

 series of thickenings which foreshadow 

 the compressed pleural rim of the larva 

 and imago. The pair of these thicken- 

 ings in the first abdominal segment 

 develop excessively, bulging out con- 

 spicuously beyond the niveau of the 

 other thickenings, so that, had I not 

 observed that the pleuropodia are 

 invaginate in this form and did not their 

 tufted secretion show clearly in the very 

 same segment, I should have supposed 

 that I had found a pair of evaginate 

 knob-like appendages. Sections show 

 that the greater development of the 

 first pair of abdominal thickenings is 

 due to excessive proliferation of the 

 hypodermal cells to form a solid succu- 

 lent mass — the oenocytes. So many of 

 the hypodermal elements are here con- 

 verted into oenocytes, that only a few 

 flattened and attenuated cells remain to 

 cover the mass externally. From the 

 surface the oenocytes may be seen shin- 

 ing through this thin covering and this 

 heightens the resemblance of the two 

 swellings to the pleuropodia of such 

 forms as Blatta and Xiphidium. The 



