1120 General Notes. [ Dec, 
enia leidyi, M. fluviatilis, M. robusta (nov.), M. milsii (nov.), M. sub- 
a 
and C. tenosperma. Mr. Potts also describes as new Parmula 
nesbyt and Meyenia minuta, from South America. The paper is > 
‘illustrated by eight well-executed process-plates of spicules, etc., 
of the species. 
Arthropod Eyes.—The first number of Dr. Whitman’s Yournal 
of Morphology contains three articles dealing with the structure 
and growth of the eyes of arthropods. The first, by Dr. J. S. 
Kingsley, treats of the development of the compound eye of 
Crangon, an abstract of which appeared in the NATURALIST for 
November of last year. Dr. Kingsley claims that the compound 
eye arises as an invaginated pit of ectoderm, and that the retinal 
layers are inverted, the light traversing them in the same way as 
in the vertebrate retina. 
The two other papers are by Dr. William Patten. The first, 
entitled “ Eyes of Molluscs and Arthropods,” is a summary of 
the results obtained by this author, and embodied in his longer 
paper in the Mittheilungen of the Naples Zoological Station for 
last year. The most important points brought out are that the 
whole of the so-called retinal elements of the compound eye are 
formed from a single-layer of cells, and that this layer has not 
been inverted, as believed by Dr. Kingsley. He also shows that 
the rhabdoms of Grenacher are in reality formed by prolongations 
of the same cells which secrete the crystalline cones. According 
to his interpretations it follows that these eyes are not adapted 
for “ mosaic vision,” but that the nerve-fibres in the crystalline 
cones are the essential light and image pércipient elements. 
Dr. Patten’s second paper deals with the development of the 
eyes of Vespa, and with some points in the structure of ocelli in 
insects. In the young embryos of Vespa the cephalic lobes pre- 
sent a thickening, which becomes pushed in and covered by an 
ectodermal outgrowth from the dorsal margin of the thickening: 
This thickening breaks up into at least six cords of cells, oo 
of which ultimately enter into the formation of the optic gangs 
a fourth (dorsal to these) probably forms the antennal lobe, pee 
the other two probably give rise to the mushroom bodies of 
brain. While the foregoing steps are in progress a second eer 
3 
= 
consists of three layers, the inner furnishing the retinal elements, 
ni ove in Cran- 
