364 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
without any previous gastrular invagination, and exhibits no signs of 
such an origin. 
Cutaneous Glands with Intracellular Canals in Hedriophthalmate 
Crustacea.* — M. M. Ide is led by his study of these glands to some 
general considerations with regard to unicellular glands. He points 
out that in all the products are passed to the exterior without passing 
into any epithelial cavity, and that no intercellular passage is formed 
by the separation of the elements. The simplest glands are epidermal 
cells, or, to speak more generally, secreting epithelial cells scattered 
among ordinary cells, and passing their products directly to the exterior. 
The caliciform cell may be taken as the type of this rudimentary form. 
In certain cases the gland-cells are developed more than their neighbours, 
and their swollen internal part extends beyond the line of the epithelial 
rows. There is thus formed a neck which connects the cytoplasm with 
the exterior. This neck forms the canal of passage for the secreted 
products, and represents in a quite simple w r ay the outer part of the 
cavity of a caliciform cell. The glandular ring on the cloaca of Avion 
presents remarkable examples of this form. In others the neck under- 
goes differentiation ; it becomes chitinized or hardened, and then takes 
on a purely conducting function, while the elaboration of the secreted 
product is localized in the swollen portion. But differentiation may go 
still further. The secreting cavity ceases to be a simple lacuna of the 
cytoplasm, and its wall becomes like that of the neck ; this is what may 
be seen in the intestinal canal of many Insects. 
The cavity may be prolonged still further and fold itself irregularly, 
without subdivisions, as in Bees, or it may take on a digitate form, or 
become richly arborescent, as it is in the segmental organ of the Hiru- 
dinea. Fresh differentiations may yet be superadded, as by the appear- 
ance of a radiate vesicle surrounding the extremity of the internal canal, 
and the radiate sheath on the external portion of the canal, as in Blaps 
viortisaga. The odoriferous gland of this species appears to represent 
the highest known degree of the differentiation of the glandular cell. 
This cell may, however, tend not only to be differentiated, but to be 
subdivided. The first indication of this is to be seen in the gland of 
the urostyle of the Oniscidse, where a deep constriction divides the cell 
into two halves, each of which possesses a nucleus. In the glands of 
Vibilia there is not a mere constriction of the cytoplasmic mass, but 
there is a true segmentation, when three cells become formed. This 
subdivision goes still further in the glands of Phronima, where there 
are five distinct cells The segmental glands of the Hirudinea appear 
to belong to the same type. 
The products of secretion of the glands of the urostyle of Oniscus form 
exceedingly fine threads very like the silk of Lepidoptera and Spiders. 
Development of Oniscus murarius and Porcellio scaber.f — M. S. 
Jourdain deals particularly with the development of the appendages of 
these two Isopods, and with the so-called dorsal organ. The egg 
becomes provided with an epiblastic shield formed of columnar elements ; 
it then elongates, and the ventral plate becomes divided by a groove into 
* La Cellule vii. (1891) pp. 347-73 (2 pis.). 
t Comptes Rendus, cxiv. (1891) pp. 428-30. 
