ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
779 
species of Pieris and three other Lepidoptera. It is colourless and 
amorphous, and is secreted by the pores of the larva after it has 
changed its skin for the last time. Its chemical formula is given as 
c 14 h 20 n 2 o 5 . 
Development of Imaginal Eye of Vanessa.* — Herr H. Johansen 
describes the facetted eye as being derived from the unilaminate 
epidermis of the caterpillar, without the intermediation of any invagi- 
nation such as has been described by Patten in the Wasp. The 
approximation of the epidermal cells to form the ommatidia occurs 
soon after the separation of the larval eye from the epidermis. The 
cavity of the cephalic vesicle contains a number of leucocytes as well 
as the destruction products of the larval organs. Thirteen cells 
primitively take part in the formation of one ommatidium ; there are 
four cells whose nuclei were called Semperian by Claparede, two pig- 
ment-cells of the first order and seven retinular cells, as well as one 
ganglion-cell and six pigment-cells of the second order. The nuclei 
of the pigment-cells of the first order primitively lie above or distally 
to the Semperian nuclei ; soon, however, the cells belonging to the 
latter secrete the corneal lenses and the crystalline-cone-segments. The 
cuticular hairs are products of cells which take no part in the forma- 
tion of the ommatidia, but which may be regarded as the last remnants 
of the epidermal cells which were primitively present in larger numbers ; 
they are indications that the phylogenetic development of the facetted 
eye of the Tracheata is due to an aggregation of single eyes. 
The eye remains, apparently, unilaminate throughout its whole 
extent ; the formation of the crystalline cone is not an external ex- 
cretion in the sense of Claparede, but an internal secretion; within 
each of the four cells a morsel of cone substance is given off proximally 
from the “ Semperian ” nucleus. The rhabdom is not an excretion of 
the cells of the retinula, but a living modification of their protoplasm, 
and it is, therefore, not a process of the crystalline cone, as Patten 
suggested. 
Pigment appears in all the cells of the facetted eye, with the ex- 
ception of the distal ends of the crystalline-cone-cells and the hair- 
cells. The epidermal cells which become grouped into ommatidia 
receive a not inconsiderable amount of pigment from the eyes of the 
caterpillar, which is brought them by the leucocytes. 
The optic ganglion of the imago is derived from that of the larva, 
and is not an absolute new formation like the epidermal part of the 
eye. The layer of nerve-bundles, however, appears to be a new forma- 
tion as it takes its origin from two primitive nerve-bundles and arises 
by continuous centripetal cleavage of these. In the other layers of the 
optic ganglion these are merely processes of growth, in consequence of 
which the whole ganglion becomes much larger and fills up the head- 
cavity. Further descriptions, with illustrations, are promised. 
Post-larval New Formation of Glandular Cells in Silkworm.!— 
Sig. E. Verson finds in the pupa stage under the hypodermis numerous 
* Zool. Anzeig., xv. (1892) pp. 353-5. 
t Bull. Soc. Entomol. Ital., xxiv. (1892) pp. 1-17 (1 pi.); Zool. Anzeig., xv. 
(1892) pp. 216-7. 
3 G 2 
