1892.] Zoology. 865 
The anlage of the proboscis forms very early ; two cells differentiate 
at one pole of the entoderm, behind this the cells gradually coalesce. 
The sheath is also entodermal. The proboscis is formed invaginated 
inside the sheath ; the cause of exvagination is to be sought for in the 
growth of the animal in length. (Reviewer does not understand 
author’s argument in this case.) Before exvagination the rostellum 
is solid; what becomes of the centre core is somewhat uncertain. 
The hooks are also of entodermal origin; further, the nervous system, 
which arises at about the same time with the rostellum, and consists of 
a double ganglion at the base of the rostellum, two lateral and one 
median anterior nerves and two lateral posterior nerves. The latter 
connect with a double ganglion on the bursa of the male. The 
ganglion cells were uni-polar. 
` Hamann’s results differ very greatly, in some particulars, from 
those arrived at by Kaiser. Kaiser’s magnificent monograph will be 
reviewed in a later issue of Tae Naruratisr.—C. W. 8. 
Onchnesoma.—Shipley has recently studied’ the anatomy of 
Onchnesoma steenstrupti, the smallest species of this boreal genus of 
Sipunculids. In correspondence with its small size (length 3 mm.) it 
is much simplified. It has no tentacles, no vascular system, a single 
retractor muscle, a single nephridium, and a not-bilobed brain. On 
account of the lack of tentacles this Sipunculid, at least, does not 
breathe by these organs, and Shipley is inclined to regard the intes- 
tine as the chief respiratory organ here. He is farther inclined to 
think that the chief function of the tentacles, when present, is to cre- 
ate currents bringing food to the mouth, and that the chief use of the 
vascular system is to extend the tentacles. 
The Hæmal Region of Echinoderms.—This portion of the 
echinoderm structure has always been a terra incognita. In the course 
of an interesting article on “ Wandering Cells in Echinoderms ”* 
(dealing with the processes of excretion throughout the animal king- 
dom) Mr. H. E. Durham says: “ The following method of regarding 
the relations of the water tube, dorsal organ, axial perihwmal sinus, 
and the madeporic or water pores has, I believe, never been formu- 
lated; it has the advantage of bringing the different arrangements 
which have been described into harmony, and will put an end to the 
battles which have been fought over the point. First of all we must 
$Quarterly Jour. Micros. Sci., xxxiii, p. 233, 1892. 
*Quarterly Jour. Micros. Sci., xxxiii, 81, 1892. 
