536 H. LYSTER JAMESON, 



Material. The examples of Thalassema neptuni that I have 

 examined were sent to me from the Plymouth Marine Biological 

 Laboratory by Mr. E. J. Allen, the director. The various con- 

 signments that I received from Mr. Allen included large and small 

 individuals preserved, some in alcohol, some in corrosive sublimate 

 (8 hrs; transferred to 70% Alcohol), and some in Kleinenberg's picro- 

 sulphuric acid, (36 hi's, transferred to 70% Alcohol). I had also some 

 chromic acid material from Plymouth, while Dr. R. F. Scharff pro- 

 vided me with a number of large examples from Valentia, Ireland, 

 preserved, some in alcohol, some in formol, and one in Flemming's fluid. 

 Many of the specimens from both localities were of considerable size, 

 the body varying in well grown individuals from 25—40 mm in length 

 and the proboscis from 16 — 30. 



I regret that it was not until after this paper had been sent in 

 for publication that I had an opportunity of studying living material, 

 during a couple of days that I spent in Plymouth. I have no doubt 

 that a careful study of the material which I preserved while I was 

 there will throw more light on some of the obscure points. At 

 Plymouth Thalassema neptuni is usually found in the holes made 

 by the bivalve Saxicava in the limestone rocks; I also dredged two 

 small examples in Turritella shells, together with numerous specimens 

 of the Sipunculoid Phascolion stromhi, in 23 fathoms, outside Plymouth 

 harbour. So far as I am aware the habit of living in dead Gastropod 

 shells has not been observed in the Echiuroids before. 



I have nothing new to add concerning the external characters 

 of this worm. 



I. Body Integument 



The body wall of Thalassema neptuni consists of an epidermis 

 with its cuticle, a cutis, an outer layer of circular muscle fibres, a 

 layer of longitudinal muscles, an inner layer of oblique muscles, and 

 finally the peritoneal lining of the spacious body cavity. 



On examination with the naked eye or with a lens the skin is 

 seen to be papillated; the papillae are as a rule irregular in form, 

 elongated in the transverse axis of the body and most highly developed 

 posteriorly. They are smallest about the middle of the body. 



The cuticle (Figs. 1, 2 cu; Fig. 2a) is continuous over the 

 whole body wall, and is pierced only by the openings of the glands, 

 the hair-like processes of the sense organs, and the cilia. In section 

 it measures 0,003 to 0,005 mm in thickness, but is somewhat thinner 



