L.M.B.Cc. TURBELLARIA. 53 
IT.—RHABDOCGILIDA. 
A. acw~A:—This group is of considerable interest 
owing to the very simple organisation of its members. 
They have no alimentary canal or digestive cavity. The 
food (chiefly Entomostraca) is secured by the pharynx and 
passed on to the parenchyma which is the assimilating- 
tissue. An otolith is constantly present. 
Family—APHANOSTOMID. 
3. Aphanostoma diversicolor, Oe. (Pl. XII, figs. 6 and 7.) 
This species occurred in tide-pools close to the Port 
Erin Biological Station. It is distinguished by the 
colouration of the anterior end. The central part 1s violet, 
due to parenchymatous contractile pigment-cells; the 
peripheral portion and the extreme tip 1s coloured yellow 
owing to yellow vacuoles in the parenchyma. This form 
is recorded from Millport and Plymouth. 
4. Convoluta paradoxa, Oe. (Pl. XII, fig. 3.) 
During July, swarms of this species in different stages 
of development occurred among drift sea-weed (especially 
Ceramia) in Port Erin Bay. 'Tide-pools also yielded speci- 
mens but not so abundantly. The most interesting point 
of its structure is the presence of brown bodies usually 
known as yellow-cells or symbiotic alge, which live in its 
tissue and largely determine its structure. 
It has been known for ten years (owing to the work of 
Geddes and others) that another species of Convoluta 
(C. schultz) contained chlorophyll, but whether the 
chlorophyll is autochromic, that is a product of the animal’s 
activity ; or exochromic, and due to symbiotic unicellular 
algge, is a question which can scarcely be considered as 
thoroughly settled. 
Geddes’ attention was first drawn to these Convoluta 
when he saw what he took to be filamentous green sea- 
