102 mk. it. 0. puxnett ox [May 21, 



this agreement in the features chiefly relied upon in classification, 

 would seem to point to a connection between the Amphiporids of 

 these two regions closer than that between those of either of them 

 and the Northern Atlantic forms. It is possible that the present 

 wave of Antarctic enterprise may bring to light fresh forms which 

 may help to settle an interesting point. 



With the affinities of the new species other than Amj)Jdporus 

 described in this paper, I hope to deal on some future occasion 

 when considering in detail the genus Drepanophords and the family 

 of the Lineidae. 



Note on the Vascular System of Metanemerteans. 



In the writings of several authors who have treated of this 

 group are to be found discrepancies with regard to the somewhat 

 important point of the relation of the lateral blood-vessels and 

 cephalic loop to the brain and the rhynchodsoum. Mcintosh ', in 

 his monograph on the British Nemerteans, states that " At the 

 ganglionic region the vessels which go to form the cephalic arch 

 pass below the commissures (i. e. brain-commissures) and unite in 

 front beneath the channel of the snout (i. e. the rhynchodaeuin) ; " 

 and his conception of the arrangement is represented by a dia- 

 gram on p. 42 of the same work and by several figures of Amphi- 

 porus among the plates. On the other hand, the excellent figure 

 representing the anatomy of Tetrastemma candidum (pi. xiv. 

 fig. 1) shows the cephalic loop entirely above the rhynchodaeum 

 and the lateral vessels passing through the nervous ring. This is 

 the condition described by Oudemans for the Metanemerteans, and 

 arrived at after studying nine members of various genera by the 

 method of serial sections. Oudemans 2 finds " in the head two 

 vessels which communicate in front, forming a vascular loop above 

 the proboscidian sheath (= rhynchodaeum). These vessels also 

 communicate within the cerebral ring, but now beneath it (t. e. the 

 rhynchodaeum)." I have been unable to find any specific state- 

 ments for the Metanemerteans with regard to these points in 

 Burger's monograph. In a previous paper 3 , however, he mentions 

 that " Die Seitengefasse vereinigt in der Kopfspitze vor dem 

 Grehirn iiber dem Rhynchodaeum eine geriiumige Kopfschlinge," 

 though here again he does not distinctly state whether the two 

 vessels are surrounded by the nervous ganglionic riug or pass 

 beneath it. Moreover, his figures are at variance with regard to 

 the last point. In his Naples monograph, Burger distinctly 

 represents the cephalic vessels of Tetrastemma coronatum (pi. ix. 

 fig. 7) and of Amphiporus virgatus (pi. vii. fig. 16) as passing 

 beneath the ventral commissure of the brain ; whilst in another 

 place (pi. xvi. fig. 16) he figures a section of the last-named 

 species showing these vessels lying upon the ventral brain-com- 



1 Loc. cit. p. 80. 

 - Loc. cit. p. 58. 

 '■' Zeitsch. fiir wiss. Zoul. 50 Bd. 1890, p. 204. 



