ANATOMY AND PFIYSIOLOOY. 
Moll. 9 
C. Semper has found in some of the dorsal warts of Onchidium an 
optical apparatus, provided with cornea, lens, and a retina, in which 
three strata — one of strings or fibres, one of bacilli, and one of dark 
pigment — can be distinguished; the stratum of retinal fibres is the 
innermost, as in the eye of the Vei'tehrata, which is not the case in any 
Evertehrafa, except Hirudo and Pecten, the eyes of which differ in other 
important points from those of Onchidium. An annulus ciliaris and a 
macula coeca are present. These eyes are supplied from the pallial 
nerves which come from the visceral ganglion of the pharyngeal ring ; 
the eyes on the tentacles from the central ganglion. The author dis- 
tinguishes the following modifications of these eyes : — 
I, The stratum of bacilli is regularly arranged like cylindrical epi- 
thelium ; a number of eyes is crowded on the same tubercle of 
the back. Onchidium verruculatum and 8 other species. 
II. The stratum of bacilli is irregularly arranged. 
(«.) The eyes are isolated, each on a special contractile, not 
retractile, tubercle; cornea consisting of two strata, 
epidermis, and cutis, as in the preceding division. 0. 
coriaceum, luteum, and glahrum ; in the last, the lens 
consists of only five cells, in the two others, of many 
more. 
(&.) The eyes are arranged in groups, either on the smooth 
skin of the back (0. amhiguum), or 3-4 on a tubercle 
(0. typhee). 
In 17 species, these eyes have been found ; in 2 species examined by the 
author they are wanting. Reis. Philippin., iii. suppl. part, 45 pp., 5 pis. 
Preliminary note by the author himself, in Arch. mikr. Anat. xiv. 
pp. 118-124. Abstract by H. v. Ihering in JB. Anat. Physiol, vi. 
pp. 135-138. 
Iiiering’s paper on the auditory organs of the Mollusca is also con- 
tained in SB. Soc. Erlang, ix. [1876-771 pp. 35-65. 
A peculiar organ of sense [?] in the Bivalve genus Yoldia is described 
by W. K. Brooks ; it is a kind of tentacle, situated above the lower 
margin of the mantle, at the base of the sipho, only on the right side, 
composed of circular muscular fibres and a strong nerve within, coiled 
up at rest, extended and moving in all directions and even entering the 
siphonal tube. P. Am. Ass. xxiii. at Hartford, 1875, pp. 80-82, with 
woodcut. 
J. Kollmann and W. Flemming discuss the vascular system of 
Mollusks, the same parts being declared by the former to be “ lacunae,” 
without proper walls, and filled with blood, and by the latter to be cells 
filled with slime. Ber. Vers. Naturf. Munich, 1877, p. 177. 
0. Posner {1. c.) supports Flemming’s opinion as to the slime-cells, and 
is disposed not to admit the presence of true capillary vessels within the 
gills, but only lacunar holes. 
In Mytilus edulis, A. Sabatier distinguishes true capillary vessels, pro- 
vided with endothelium and lacunar capillaries without endothelium, the 
latter chiefly in the venous part of the vascular system. Ann. Sci. Nat. v. 
No. 1 . ‘ 
