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segment. Each cluster of these cells is ventro-lateral in position. The 
cells are rounded or somewhat oval in form with a granular and very 
deeply staining cytoplasm, and each cell is bounded by a clearly defined 
membranous investment. Numerous large vacuoles are generally 
present and when viewed in sections they give the cells the appearance 
of being penetrated by intra-cellular canals. Each oenocyte has a very 
prominent nucleus containing chromatin strands situated towards the 
periphery, and a deeply staining nucleolus is also present. 
The small oenocytes are very numerous and, moreover, have no 
definite arrangement though they are sometimes found in pairs 
(Figs. 22 and 27). They occur just beneath the hypodermis in the 
neighbourhood of each group of the larger oenocytes, and are mainly 
situated anterior to the latter, but they also occur in some numbers 
along the floor of each segment on either side of the nerve cord. They 
have a similar marked affinity for staining reagents and frequently each 
contains a clear vacuole (Fig. 22). A nucleus with a central nucleolus 
is present, and these cells are easily distinguished from the surrounding 
fat-body by their definite outlines and their staining properties. They 
occur in the first seven abdominal segments, a few are also present in 
the eighth but none were to be discovered in the last segment. 
The embryonic development of the oenocytes has been studied by 
Graber, Heymons, Heider, and Wheeler. They arise by a proliferation 
of the ectoderm just behind the tracheal invaginations, and similar 
metameric cell-clusters have also been observed by Tichomiroff in the 
embryo of the “silkworm.” 
Wielowiejski (1886) was the first to devote special attention to these 
cells and the name oenocyte is due to him. He pointed out their 
resemblance to the blood corpuscles, to the fat-body, to the pericardial 
cells, and to the light-pi’oducing tissue of the phosphorescent organs 
and classified these different elements together under the category of 
blood tissue. In his paper he describes the oenocytes in various orders 
of Insects, but unfortunately his account is not accompanied by any 
figures. Among the Culicidae, he refers briefly to their occurrence in 
the larvae of Sayomyia ( Corethra ) plumicornis and Culex pipiens. In 
the former he mentions that they are of two kinds, the large and 
small oenocytes, and that they are situated between the cells of the 
outer layer of the fat-body. They are restricted to the abdominal 
region and are collected together into segmentally repeated groups 
(1886, pp. 516—17). In the Culex larva he describes their occurrence 
as follows: “ Die kleinen Oenocythen liegen auf der der Leibeshbhle 
