I I 6 NEMERTINEA 



CHAI 



chief power of regeneration is situated in the head, as, if a verj 

 short piece be broken off the anterior end of the body, it vei 

 rapidly reproduces itself into a new individual. The hind 

 end of the original body often lives for a considerable time, 

 but it does not in most cases appear to possess the power of 

 reproducing a head, and after existing for a time it dies. For a 

 while, however, it so far retains its vital powers that the gener- 

 ative products continue to grow, and actually attain to perfection. 

 Severe wounds also heal very quickly and completely, and all 

 local injuries are speedily repaired. 



Owing to the force with which it is shot out, the proboscis is 

 often completely severed from the body, and in such a case the 

 animal grows a new one in an extremely short space of time, 

 The proboscis thus broken off retains its power of movement 

 and contractility for a considerable time, and has been more than 

 once mistaken for a worm. This great vital power is probably 

 due to the great development of nervous tissue, the proboscis 

 being usually richly supplied with nerve plexuses. 



One large form, Zineus sanguineus, seems to possess great 

 recuperative powers. It shows a marked tendency to break up 

 into pieces, when not only the head end, but also the other 

 portions develop into perfect animals, each one growing a 

 head and all the organs belonging to it. Thus in this case an 

 animal may multiply by a simple process of transverse fission, 

 and form numerous complete individuals. 



Breeding. The breeding season only appears to cease in 

 the extreme of winter. Different genera and species seem to 

 mature their generative products at different times. 



In the armed Nemertines the eggs are deposited separately, 

 and are not connected together except by such accidental mucus 

 as the animal deposits normally ; but in the unarmed a special 

 mucous secretion forms a thick investment for the eggs. 



M'Intosh x has observed the process of the deposition of the 

 male and female products in Nemertes gracilis. He put into a 

 glass vessel a male and female of this species in which the 

 products were apparently ripe. Soon spermatozoa began to issue 

 in wreath-like jets from the body of the male, at first from the 

 middle region of the body, and afterwards anteriorly and pos- 

 teriorly, until the animal was enveloped in a dense cloud of sperma- 



1 Loc. cit. 



