I 10 



NEMERTINEA 



Order I. Hoplonemertea. 



The proboscis is armed. The epidermis rests on a thick lay< 

 of connective tissue plentifully supplied with glands, below which 



is a prominent basement membrane. 

 The muscular layers of the body are 

 two in number, an outer circular and 

 an inner longitudinal. The nerve- 

 trunks lie within the muscular layers 

 of the body and give off regularly- 

 arranged branches. There is no 

 nerve plexus. Each of the cephalic 

 slits generally opens by a pore situated 

 in the centre of a transverse groove, 

 which is beset along one side by a row 

 of shorter grooves at right angles to it. 

 Fig. 57. Anterior end of the The apparatus consists of a ciliated 



everted proboscis (Hoplone- i j i i ^ 



mertea). g.p, Glandular por- duct surrounded by nerve tissue, and 

 tion of the proboscis ; U, lateral passing into lobes of tissue which are 



sacs containing stylets; m.p. Ll .,, . , , . , .-,*, 



muscular portion of the pro- connected with the brain by thick 

 boscis ; *, stylet ; s.b, granular nerve-cords. The mouth opens rather 



basal portion of stylet. . \ . 



lar forward m iront ol the bram. 

 The intestinal pouches are symmetrically arranged. Auditory 

 organs are said to exist in some forms, consisting of vesicles 

 containing otoliths. The vascular trunks are connected an- 

 teriorly by closed vessels and not by lacunar spaces. 

 The principal British genera and species 1 are : 



Amphiporus bioculatus M'Int., A. dissimulans Riches, A. hastatus M'Int., 

 A. lactifioreus M'Int., A. pulcher Johnst. 



Drepanoplwrus rubrostriatus Hubr. ( = A. spectabilis Qtrf.). 



Tetrastemma ambiguum Riches, T. candidum 0. F. Mull., T. dorsale Abildg., 

 T.jiavidum Ehrenb., T. immutabile Riches, T. melanocephalum Johnst., T. 

 nigrum Riches, T. robertianae M'Int, T. vermiculatum Qtrf. 



Prosorhochmus claparedii Keferstein. 



Nemertes carcinophila Koll., N. gracilis Johnst., N. neesii Oerst. 



Malacobdella grossa O. F. Mull. 



1 Our knowledge of British species is mainly due to M'lntosh {British Annelids, 

 Ray Society, 4to, 1873) and Riches {Joum. Mar. Biol. Ass. vol. iii. 1893-1895, p. 1. 



