354 Prof. Mialland Mr. R. Shelford on the Structure and 
brates, contains scattered cells or collections of cells 
which may discharge mucus, fibres, and nuclei.* 
All insects which have been anatomically studied seem 
to agree in the possession of numerous blood-cells, 
which may float in the blood as corpuscles, or form sheets 
and solid masses in the blood-cavities. The yellow 
cenocytes described by Wielowiejski,t the pericardial 
cells, and the fat-body, answer to this description. The 
pericardial cells and the fat-body are believed to be 
peculiar kinds of coelomic epithelium, but the cenocytes 
arise from the ectoderm. In Hydrophilus groups of 
parastigmatic cenocytes have been traced to invaginations 
of the ectoderm.{ Such structures may be rudimentary 
analogues of the cellular cords, which attain such an 
extraordinary development in the larva of Phalacrocera.§ 
Kowalewsky|| finds that in certain Orthoptera (Pachy- 
tylus, Locusta) Malpighian tubules penetrate the heart, 
entering by the cardio-ceelumic apertures which he has 
described, becoming much convoluted, and ultimately 
reaching the pericardium through the cardio-pericardial 
apertures. Here the motive seems to be, not nutrition 
at the expense of the blood, but purification of the blood 
itself, for which a large surface of contact is equally 
necessary. 
We must now attempt some physiological interpreta- 
tion of the cellular cords in the heart of Phalacrocera. 
We do so in a very guarded manner, feeling the 
difficulty of the task, and the necessity of a more 
searching inquiry than we have been able to undertake. 
It seems to us unlikely that the cords of Phalacrocera 
serve any such purely mechanical function as is ascribed 
by Michaelsen (see above) to the cellular rod of the 
Enchytreidz. Numerous and large nuclei would not be 
required in a tissue which has no more complex function 
than to stop up a cavity. Nor does any such mechanical 
“ Waymouth Reid, The Process of Secretion in the skin of the 
common Eel, Phil. Trans., Vol. 185 (1894), and authors there cited. 
i Zeitschr. f. wiss. Zool., xliii., pp. 512-536 (1886). 
¢ Graber, Biol. Centralbl., xis, "pp. 212-224 (1891). 
§ Weismann’s « garland- shaped cellular cord” (Entw. d. Dip- 
eon. p. 132, pl. vii., fig. 10) may possibly be a structure of the 
same kind. See also Pantel on Thrivion larva (CRs 189751 
pp. 472, 580). 
|| C.Lt., cix., pp. 409-411. 
ay 
