1084 The American Naturalist. [November, 
The Arthropod Eye.—Dr. Patten,? from a study of the eyes in 
several hexapods, concludes that ‘‘ the convex eye of arthropods is a 
group of hair-bearing sense buds.’’ New facts are presented regard- 
ing the eyes of Belostoma, Tabanus, and Vespa, and the following 
additional conclusions are drawn: The so-called pseudocone is the 
homologue of cuticular sense hairs ; between the ommatidia occur hair- 
cells, which are surrounded by pigment, ‘‘so that they bore a very 
striking resemblance to ommatidia, and probably functioned as such.” 
As a corollary the pseudocone type is the most primitive. Watase’s 
view is regarded in this light as erroneous, the development of Vespa 
showing that there is no bending of the retinula cells. Patten thinks 
that a “ telescoping ” rather than an invagination must be invoked to 
explain the features of the arthropod eye. Corrections are made of 
former statements as to the relationships of the corneagen cells to the 
spindle (rhabdom), and the formation of the corneagen in Vespa. 
Molluscan Notes.—Canon A. M. Norman, the English student 
of the invertebrata, has begun in the Annals and Magazine of Natural 
History a revision of the British mollusca. 
It may interest conchologists to learn that the somewhat rare mollusc 
Zirfea crispata occurs abundantly at Salem, Mass., at a spot where it 
is easily accessible at low tide. The locality is in a bed of indurated 
clay, about midway between the ** neck ’’ and the beacon on the neck 
bar. At low tide they are covered by but two or three inches of water. 
The Origin of Vertebrates.—Two recent papers attempt to 
find the ancestors of the vertebrates in the arthropods. The first, 
by Dr. William Patten,’ recognizes this ancestor in the arachnids. The 
nervous system is compared throughout with that of vertebrates, and 
some startling homologies are brought out, embracing not only general 
relationships but exact correspondences in minute details of sense 
organs, segments, nerves, etc. The vertebrate mouth arises as a 
modification of the dorsal organ, the notochord from the the mittel- 
strang of the arthropod nervous system, the cranium from the entoster- 
nite, the gill slits from nephridia; the pectoral fins are homologous 
with the scorpion pectines! Aside from these speculations the paper 
contains a number of observations on the embryology of scorpions 
and of Limulus. 
? Anat. Anzeiger, V., p. 353, 1890. 
3 Quar. Jour. Micros. Sci., XXXL, p. 317, 1890. 
