THE MARINE TURBELLARIA. 309 



of the special features of the gut-branches of the Pseudoceridae (viz. dorsal diverticula of 

 Thysanozoon, marginal pores of Yungia) are paralleled in the Planoceroids and in Polyporus. 



Starting from a hypothetical, primitive, non-tentaculate form such as Anonymus, there is 

 no difficult}' in deriving both the Cotylea and Acotylea from it, if we admit that the tentacles 

 in the two groups are homologous. There is no difficulty in supposing the margin of the 

 body to have coalesced in front of the tentacles, and these latter to have moved back 

 carrying their eyes with them, and come into connection with the dorsi-ventral muscles. As 

 will be seen, this theory accounts readily for the presence of eye-spots in connection with 

 nuchal tentacles. 



There is a possibility that some of the more primitive Acotylea may be directly descended 

 from forms that have never developed tentacles, but evidence on this point is lacking. On 

 the whole I think that the balance of evidence inclines strongly to the view I have here 

 advanced, which has the advantage of being better correlated with what is known of the 

 anatomy of the groups 



Natural History Notes. I append some interesting notes given me by Mr Gardiner: — 



" All the forms were preserved with HgCL ; but, however much they may be expanded, 

 all contract when the corrosive sublimate solution is poured on them, hot or cold. Anaesthe- 

 tization by cocaine was useless, for, without keeping the animal quiet and expanded, it 

 caused the excretion of a large quantity of mucus and this prevented the fixing fluid from 

 getting at the tissues. Usually in cocaine, too, the animal began to rot and break up before 

 it was sufficiently quiet to be killed. Chloral hydrate seemed to have little effect and alcohol 

 did not begin to act for some hours, and as soon as the animal became quiet it began 

 to secrete mucus, a fatal difficulty. The best way to preserve would be, I believe, to drop 

 specimens straight into a bottle of HgCla on the reef itself or into strong — at least 10 per 

 cent. — formaline, removing after 15 — 30 seconds into concentrated corrosive. 



" It is almost impossible to get the Thysanozoons off the rocks, as they break up readily. 

 With all forms the only really effective way is to tease them and make them project them- 

 selves into glass tubes. A large Thysanozoon (?) secreted an enormous amount of mucus, and 

 broke up rapidly into separate pieces ; its mucus collected a large amount of dirt, and killed 

 the other animals in the bottle. It also extruded a quantity of faecal matter. The smooth- 

 skinned forms do not secrete so much mucus, but really each form requires to be placed at 

 once and killed in a separate vessel. 



" I carefully examined for the food of these Platyhelminths and found them browsing on 

 Tunicate colonies and sponges, whilst others had been eaten by them under the same stones. 

 Weed was not generally touched, but dead animal-matter laid down under stones proved an 

 attractive bait. They do not browse on Gylicia, Goenopsammia, nor any of the corals whose 

 normal habitat is their own. Hydrozoa and Actinia too are not touched. Often at Hulule 

 I turned over rocks which had Tunicate sponges and colonies of hydroids; but it was only 

 the Tunicates that were generally attacked, the sponges being rarely touched. 



"The Turbellaria live principally under stones and rock, especially where the latter is 

 lying freely upon the reef Sand is deleterious, and, if much of it is present, no forms will 

 be found. When a rock is overturned the Planarians hurry off in all directions, some over 



' I am aware that the embryological method lends no support so far as I know to this view, but neither does it 

 make for either of the alternatives. 



