1890.] Zoology. 583 
end of the glandular portion of the nephridium, This latter portion 
runs backward beneath the pericardium until it reaches the posterior 
adductor muscle, It then bends upward and enters a three-chambere 
portion lying in the angle between the pericardium and posterior 
adductor. From thence the organ runs forward parallel to the glan- 
dular portion, until, at about the level of the nephrostome, the ureter 
goes downward and outward to the exterior. The histological charac. 
ters of the different portions are described. In returning from the 
"` different portions of the body the blood mostly enters the sinus venosus, 
but some goes directly to the chambered portion of the nephridium. 
That which enters the sinus can pass through numerous openings, so 
as to bathe the external surface of the nephridial cell-walls. By care- 
ful maceration with nitric acid, Dr. Rankin traced the nerve supply of 
the organ, and finds that it receives an anterior innervation from the 
cerebro-visceral commissures, and a posterior from the visceral gan- 
glion. The question of the taking up of water is discussed. Dr. 
Rankin describes the valves in the course of the circulatory organs, 
and thinks that their position and mode of action is sufficient to 
explain all the phenomena of expansion of the foot, etc., without re- 
course to the absorption of water. 
The Dorsal Papille of Nudibranchs.—Dr. W. A. Herdman 
enumerates‘ three types of projections upon the dorsal surface of the 
Nudibranch molluscs. These are (1) the dorsal tentacles (Rhino- 
phore) ; (2) the true branchiz, and (3) the dorsal papilla (Cerata), 
The last—Cerata—are regarded as outgrowths of the epipodial ridge, 
and frequently are considered as organs of respiration. They may be 
divided into those which contain diverticula of the liver (hepato- 
cerata), and those which are mere outgrowths of the body wall (parieto- 
cerata). Dr. Herdman thinks that these cerata play at most but a 
moderate part in respiration, and thinks this is shown by the fact that 
they coëxist in many forms along with the true branchiæ, and that in 
all cases they contain no more numerous blood vascular spaces th: 
does the adjacent skin. On the other hand, he regards them as pro- 
tective either by causing the animal to resemble closely its surround- 
ings, or, as in the case of Eolis, by making the animal conspicuous, 
and warning all fishes, etc., to let it alone because of the stinging 
organs in the cerata. These last are described and figured. The 
hepatic cæca extend a considerable distance into the tentacle, and 
then are continued directly into a ‘‘ connecting tube,” which in turn 
opens into the cnidiphorous sac, which is evidently an invagination of 
t Quart. Jour. Micros. Sci., XXXI., p. 41, 1890. 
