150 Royal Society : — 



along the single dorsal vessel of the anterior region. On arriving 

 at the base of the snout the vessel ends in the efferent branch to 

 the tentacle on each side. The current rushes along the latter 

 (nearly at right angles to the dorsal trunk) to the tips, sending off 

 in each a web of circiimferential capillaries throughout the greater 

 part of its length, and terminating in the afferent vessel, which pro- 

 ceeds 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 Magelonce which are provided with the con- 

 voluted lateral organs of the body, mentioned further on, in autumn. 

 The cephalic vessels are much abbreviated, and the direction 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 con- 

 trol of the greatly developed muscles of the body-wall. Thus 

 it happens, as formerly indicated, that the contraction of the latter, 

 and of the special muscular apparatus which closes the communi- 

 cation with the posterior region at the ninth segment, drives the 

 blood forward to unroll the proboscis. This muscular arrangement 

 in the anterior region and the muscular walls of the vessels them- 

 selves 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. Li each segment a lateral branch leaves the 

 ventral 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 Midler, 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 on\Aard 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 youifg salmon and other translucent 

 vertebrates. When examined in the liquor sanguinis of the living 

 animal (as in a favourable view of a healthy tentacle) the blood- 

 corpuscles show a pale nucleus. 



i{,;rvous Sifstein. — The central mass of the nervous system lies in 

 front of the preoral chamber in the fork of the median muscles, 

 and consists of the ordinaiy ganglion-cells with connective-tissue 

 bands. No eyes or other sense-orgaus exist, though the animal is 

 extremely sensitive to light and other stimuli, and lives in regions 

 where there is abundance of sunshine. Two main nerve-trunks* 

 proceed backward in the hypoderm — at first outside, then under, 

 and finally to the inner border of the ventral longitudinal muscles. 

 At the commencement each is accompanied by a neural canal (the 



