218 DISCOVERY REPORTS 



and So on, for work later, since there was little time for section cutting and no oppor- 

 tunity for consulting the literature of the group. The ultimate preserving fluid was 

 75 per cent alcohol for nearly all specimens, but I found that fixation in Da Fano i 

 (cobalt nitrate and formalin — see Lee, 1928, p. 348) and subsequent preservation in 

 5 per cent formalin worked well with Linens corrugatus, especially the large red-brown 

 form, which does not bleach as readily with this treatment as it does in spirit. Chloral 

 hydrate was the usual anaesthetic. The crystals were added to the sea water in the Petri 

 dish containing the specimen. I found that small forms could be dealt with by sucking 

 them into a glass tube rather smaller in bore than their diameter and holding the tube 

 under hot water running from a tap. When the worms were blown out of the tube into 

 the fixing fluid they contracted very little and not only kept fairly straight but often left 

 their protective mucous coat in the tube and thus facilitated the subsequent examination 

 in cedar oil for deeply embedded eyespots. Bouin and Bouin Duboscq were frequently 

 used as fixing reagents. Corrosive sublimate both hot and cold was tried but was not 

 successful. On one occasion large specimens of Linens corrugatus were immobilized by 

 the natural freezing of the surface layer in the basin left overnight outside the station at 

 South Georgia. The animals were by no means dead although they were at first com- 

 pletely insensitive. As mentioned later in the notes on this species, the slackened mus- 

 culature of the semi-frozen animals threw light on differences that had been noticed in 

 the body form of preserved specimens. 



When the material from the ships was being worked over the numbered series was 

 continued, since very few of the specimens could be identified at sight ; and it was used 

 throughout in the numbering of the serial sections. The slides were marked with a 

 diamond N 1, N 2, N 3 and so on, in addition to the serial number in each particular 

 series, and the number was, of course, added to the label replaced with the remainder 

 of the specimen. 



The pelagic forms were fixed and preserved in 5 per cent formalin. Before sections 

 were cut the preserved specimens were measured and examined for form, colour and 

 markings. Eyespots were sought for by clearing in cedar or anilin oil. In the armed 

 species the armature was especially looked for, and variations in the number of stylets 

 noted. 



Identification with previously described species has, however, not been an easy 

 matter, for variations occur in certain characters that have been used for specific de- 

 termination, for instance, in the number of nerves in the proboscis and the size of the 

 armature. The state of contraction of the body affects the relative thickness of the body 

 layers and the course of the lateral nerves when they leave the brain. Even the shape of 

 the brain and the position of the organs in relation to it can vary from this cause, though 

 I do not know to what extent. Body form and colour vary considerably in some forms, 

 the outstanding example being L. corrugatus, which appears to be the L. ruber of the 

 south, judging by the colour differences between individuals that it exhibits when alive 

 and the changes in body form that take place on fixation. If there are difficulties of 

 identification with live animals there are greater difficulties with preserved specimens 



