520 CRESSWELL SHEARER. 



placed in small watch-glasses of sea water the worms after a 

 short time throw out a considerable quantity of mucus, which 

 hardens about them forming a firm capsule, coiled up inside 

 of which the worm can be plainly seen. The capsule soon 

 loses its bright red colour, when it is quite indistinguishable 

 against any small piece of alga to which it may be attached. 

 This year towards the end of the season I noticed a number 

 of males settling on small pieces of sea-weed and coiling up ; 

 they remained in this position for several days, when they 

 seemed to have secreted a certain amount of mucus about 

 themselves. These worms may possibly have been under- 

 going encystment ; I was unable, however, to keep them 

 long enough to determine their ultimate fate. As the worm 

 during the encapsulated condition easily escapes observation 

 as the result of its minute size and lack of colour, it can 

 readily be understood how this encystment might account 

 for their periodical disappearance. The mucus thrown out 

 by the worm is evidently derived from the clear large cells 

 that have been frequently noticed in the epidermis. These 

 cells answer to all the usual staining reactions for mucus. 

 They recall similar cells seen in a large number of Tur- 

 bellaria, and this power of throwing out mucus to form a 

 capsule is perhaps another point of resemblance between the 

 two groups. In Histriobdella,^ a form closely related to 

 Dinophilus, and usually classed with it in the group of the 

 Archiannelida, I have observed that the female in laying its 

 eggs surrounds each egg with a mass of mucus which subse- 

 quently hardens about it, securely fastening it in a stalked 

 capsule to the eggs of the lobster on which this animal lives 

 parasitically. Inside this capsule the embryo undergoes its 

 entire development, only emerging in the adult state. 

 Among the Turbellaria a number of forms also lay their 

 eggs in somewhat similar fashion, as, for instance, Lepto- 

 plana, Plagiostomum,^ and numerous parasitic forms. 



' I follow Haswell (9) in retaining the name His trio bdel la instead of 

 Foettinger's (4) modification Histriodrilus. 

 ' See Bresslau (2), figs. 73 and 74. 



