PROGRESS OF MICROSCOPICAL SCIENCE. 259 
each a web of circumferential capillaries throughout the greater part 
of its length, and terminating in the afferent vessel, which proceeds 
backward, collecting, as it goes, the capillary streams, and then ends 
by turning forward at the base of the snout as the efferent cephalic 
vessel. The latter has no evident capillaries, but bends round at the 
tip of the flattened organ to terminate in the afferent cephalic vessel. 
A curious change takes. place in the majority of those Magelons 
which are provided with convoluted lateral organs of the body, in 
autumn. The cephalic vessels are much abbreviated, and the direc- 
tion of the current at the base of the snout is somewhat modified. 
The blood from the head and anterior region collects into a series of 
large vascular meshes which occur in the anterior region of the body, 
and in which the current is for the most part under the control of the 
greatly developed muscles of the body-wali. Thus it happens that 
the contraction of the latter, and of the special muscular apparatus 
which closes the communication with the posterior region at the 
ninth segment, drives the blood forward to unroll the proboscis. This 
niuscular arrangement in the anterior region and the muscular walls 
of the vessels themselves at the posterior part of the same division of 
the body send the current through the relaxed barrier at the ninth 
segment into the muscular ventral blood-vessel of the posterior region, 
and onward to the tail, where the trunk ends by bifurcating into the 
two dorsal vessels. In each segment a lateral branch leaves the ven- 
tral trunk at the anterior dissepiment, turns round and _ proceeds 
backward to the next dissepiment, and terminates in the branch to the 
dorsal vessel. Further, as first observed by Dr. Fritz Miiller, a sac- 
like dilatation takes place shortly after the commencement of the 
latter, and it fills at intervals, the distention being followed by a 
contraction which sends the blood onward by the branch to the dorsal 
vessel. In vigorous specimens, the currents of the blood are as swift 
and beautiful as in the tails of young salmon and other translucent 
vertebrates. When examined in the liquor sanguinis of the living 
animal a distinct nucleus can be seen in the blood-corpuscle. 
Professor Leidy on Rhizopods.—Professor Leidy, whose observa- 
tions on those animals we have from time to time recorded in these 
pages, has lately read a paper containing further results, before the 
Philadelphia Academy. This paper is abstracted in ‘Silliman’s 
Journal’ for March. It seems that Professor Leidy stated that last 
July, in the sphagnum swamps of Tobyhanna, Pocono Mt., Monroe 
Co., Pa., he noticed an abundance of a Rhizopod which he thought he 
had not previously seen, and which he at first supposed to be an un- 
described species, but which he now viewed as a variety of Hyalo- 
sphenia ligata. From this, as previously described, it differs in the 
test being of a pale sienna colour, and perhaps of greater thickness, 
but otherwise is like it. The test is compressed pyriform, with the 
length and breadth nearly or about equal, and the thickness one-half. 
The lateral borders are obtusely rounded. The mouth is transversely 
oval. The sarcode is colourless, and attached to the inside of the 
test by diverging threads. The pseudopods are usually from two to 
three. Measurements, ‘08 mm. long and broad, and ‘036 thick, with 
