326 Mr. W. C. Minor on Natural and Artificial Section 



sions beneath the skin, germs of hooks and hairs appear ; and the 

 pulsations of the artery are evident while the food forces a way 

 through them. The hooks and hairs gradually come through 

 the skin in succession from before backward, while, the rings 

 enlarging, the Naid increases considerably in length. While in 

 this way new segments and their contents are forming within 

 the anal ring, on the other side [anteriorly] of it a strongly 

 marked transverse line, different from those just mentioned, ap- 

 pears, and extends across the whole width of the animal. The 

 angles formed at the sides of the body project, and on the top 

 a slight projection is evident, which gradually becomes a distinct 

 proboscis, while, finally, eyes appear back of this fission. Thus 

 the Naid becomes a mother.". ..." Frequently one may see in 

 the anterior half of the elongated anal ring of the mother Naid 

 a second ring-formation similar to the one just described.". . . . 

 " This is not all. Hardly has the second bud acquired the length 

 of one mature ring than a third bud appears before it ; and I 

 have even seen a fourth.". . . . "Further, not only may a parent 

 and its four offspring thus appear, but the buds themselves may 

 give rise to new buds, their terminal joints forming new buds as 

 they themselves were formed. Hence we may find a parent with 

 its children and grandchildren attached to its body." [Op. cit. 

 pp. 34, 36.) 



Miiller afterwards gives his observations upon a single Naid 

 from the 20th of May to the 9th of June. During this time it 

 gave off the buds observed posterior to the 17th pair of combs, 

 after which a formation of rings began, without any trace of 

 separation, until the body was elongated to over 40 pairs of 

 combs. About this time a fission occurred between the 21st 

 and 22nd pairs of combs. Fission occurring in this way after 

 an elongation of the body I shall speak of as the "renewal of 

 fission." Further observation of individual Naids led him to 

 conclude that each bud is formed one joint anterior to its pre- 

 decessor, that there is thus a gradual reduction of the parent 

 segments till a certain point ; that then a re-formation of rings 

 takes place, and an elongation of the body of the Naid to re- 

 commence this circle of fission. 



Schultze, in his article " Ueber die Fortpflanzung durch Thei- 

 lung bei Nais proboscidea" (Archiv f. Naturgeschichte, 1849, 

 t. XV. p. 293) confirms the statements of Miiller as to the passage 

 over of one of the parental segments to each bud*, though he was 

 not fortunate enough to observe the recommencement of fission 

 in the elongated Naid. He observes also (p. 301) that, contrary 



* Leuckart at first doubted the correctness of this view (" Ueber die 

 ungeschlechtliche Vermehrung bei Nais proboscidea," Wiegm. Arch, 

 J867), but has since been convinced of its justice. 



