40 HISTORY OF THE SUBJECT, 



anus." The early structural observations of Dr. Johnston are also reprinted from ' Loudon's 

 Magazine/ the ' Magazine of Zoology and Botany/ &c, with the plates, and quotations made 

 from the work of Sir J. Dalyell. It would not be just to state that this treatise advances British 

 science ; but much must be overlooked in the circumstances of its publication. Its value chiefly 

 lies in being the only English work on the subject. 



Dr. Baird, in the 'Proceedings of the Zoological Society for 1866/ 1 gives an account of a 

 new species of Monoecious worm, which is evidently one of the Anopla allied to the Gordius fragilis 

 of Sir J. Dalyell (Cerehraiulus angulatus) , with the margins of the body produced as in the swimming 

 forms. The author stated that the ventral slit led into the " visceral cavity/' and agreed with many 

 others in regarding the proboscis as the alimentary canal, and its aperture in front, the mouth. 



The observations of Mr. Alex. Agassiz 2 carry those of the experienced Prof. Loven 3 a stage 

 further with respect to the development of a curious larva, which the former regards as 

 Nemertean. The most remarkable feature is the discovery of a kind of retrograde metamor- 

 phosis which the young animal undergoes, whereby it loses its segmented form and its tentacles, 

 and assumes the simple outline (but not the structure) of a Nemertean. Further remarks on 

 this interesting communication will be found elsewhere. 



In 1867 the author published a short paper on the Gregariniform Parasite of Borlasia. 4 

 The occurrence of this parasite was observed in several species, together with certain other 

 parasitic ova in gelatinous mucus, which occupied the alimentary tract of the worms. Pseudo- 

 navicellse were also mentioned. Various notes were further communicated in the author's 

 Reports to the British Association. 5 



Professor Keferstein in 1868 made known the singular fact that, in one of the Enopla from 

 St. Malo, he had found the anterior generative sacs filled with spermatozoa, and the posterior 

 with ova ; thus establishing the occurrence of hermaphroditism in this formerly dioecious group. 6 

 A P. Marion, the following year, observed the same fact, also in one of the Enopla — from deep 

 water off Marseilles. 7 This species had four eyes, each furnished with lenses ; and it differed 

 from that described by Keferstein further in not having the male and female organs arranged 

 in separate parts of the body. 



In the same year, a paper on the reproduction of lost parts in the Nemerteans was com- 

 municated by the author to the Linnean Society. 8 In this it was shown that each of the 

 fragments into which Linens sanguineus breaks becomes a perfect animal. Allusion was also 

 made to the curious manifestation of acidity presented by the majority of the Nemerteans, and a 

 few exceptions noted in a paper on the boring of the Annelids. 9 



1 ' Proceed. Zool. Soc./ Peb. 13, 1866. 



2 " On the Young Stages of a few Annelids/' ( Ann. Lyce. Nat. Hist. N. York/ vol. viii, June, 1866; 

 and ' Ann. Nat. Hist./ 3rd ser., vol. xix, p. 208. 



3 ( Ann des sc. nat./ ser. 2, xviii, p. 288. 1848. 



4 ' Journ. Micros. Sc./ vol. xv, n. s., Trans., p. 38, pi. ii. April, 1867. 



5 f Kept. Brit. Assoc./ 1867, p. 92; and < Rept. Brit. Assoc./ 1868, p. 340. 



6 < Archiv fur Naturges./ 1868, p. 102, taf. 3, f. 1 and 2; and < Ann. Nat. Hist./ ser. 4, vol. i, 

 p. 229. 



7 ' Ann. Nat. Hist./ ser. 4, vol. iv, p. 136. 



8 < Proceed. Linn. Soc./ Zool., vol. x, pp. 251—253, tab. 7. 

 y < Ann. Nat. Hist./ ser. 4, vol. ii, p. 293. 



