466 WESLEY R. COE AND STANLEY C. BALL 
The parenchyma is limited to relatively small areas which lie 
between the multitudinous muscle bundles. Interspersed among 
the areas of parenchyma are very numerous blood lacunae. 
Conspicuous nerves leave the lateral nerve cord in the region 
of the tentacle and extend the entire length of the organ, sending 
numerous branches to the musculature and presumably also to 
the integument. There are two main tentacular nerves, one lying 
dorsally and the other ventrally in the median vertical plane. 
Function. The presence of these large nerves led Birger (’09) 
to believe that the function of the tentacles was sensory, and this 
office they probably have to a certain extent. Their main func- 
tion, however, seems obvious, now that we know that they de- 
velop only in the male sex, and there only coincidently with the 
sexual maturity of the individual. 
The tentacles are, we must remember, associated with cephalic 
gonads small in number, the spermatozoa of which are used to 
fertilize‘a very small number of eggs in the female. Hence with 
this restriction in the number of possible offspring from a pair, 
there must be the greatest requirement that fertilization should 
always be successful. Nature cannot in this case afford such a 
waste of sexual products as occurs in other nemerteans where 
thousands of times as many gametes are produced by each indi- 
vidual. Therefore comes the advantage of an act of sexual union 
to provide the greatest assurance of insemination. 
The tentacles meet this requirement in providing the sexually 
mature male with a pair of strong muscular appendages which 
enable him to cling to the female until her eggs have been ferti- 
lized. This clinging instinct doubtless accounts for the fact that 
the males are so much oftener secured than are the females, for 
the former use their tentacles to cling to other objects, such as 
nets and fishing lines. In this instance the tentacles are of course 
unadaptive, but that does not invalidate their general adap- 
tiveness, for nets and lines are not natural to the animal’s 
environment. 
