198 Copepoda living as Parasites or Messmates. [Sess. 



Copepoda, including some curious species, are also associated 

 with Ascidians of various kinds, but they are so numerous 

 that the consideration of them would require a separate paper. 

 I may also state that the remarks which follow will, for 

 the most part, be restricted to species that have come under 

 my own observation. 



1. Copepoda usually fov/iid on sponges as commensals or mess- 

 mates. — The two sponges on which I have most frequently 

 found Copepoda are Chalina oculata, a soft, branching species, 

 not uncommon on the pier at Granton ; and Siibcrites domun- 

 cula Olivi, or Hymeniacidon suberea as the name is in Bower- 

 bank's monograph. The Copepoda found on these sponges 

 appear to belong exclusively to the family Asterocheredse. 

 Asierochercs Boccki (Brady) is the species common on Chalina. 

 I usually obtained these Copepods by washing the sponge in 

 moderately strong methylated spirit. Two different species of 

 Asterocheres are found on the Suberites — viz., Asterocheres 

 echinicola and Asterocheres suberea. Suberites domuncida is a 

 moderately common sponge ; it is massive and compact in 

 structure, and is frequently somewhat globular in form. In a 

 large proportion of the sponges examined a molluscan shell — 

 usually a univalve of some kind — was enclosed within their 

 substance, and they also contained a cavity in which a hermit- 

 crab found shelter. The sponge, therefore, has not always an 

 evenly rounded surface, but frequently presents the appearance 

 of a potato ; and so closely do many of them bear this re- 

 semblance that I have sometimes heard them spoken of as 

 " Sea -potatoes." Numerous water -passages penetrate the 

 substance of the sponge, and it is in the largest of these that 

 the Copepods live. If one of the sponges be cut so as 

 to expose a longitudinal section of these passages, the Copepods 

 may be seen adhering to their sides or partly filling the 

 openings of smaller passages branching off from the main ones. 

 As the Copepods are small and of the same colour as the 

 sponge, they require to be carefully sought for. I am not 

 certain whether the Copepods are found only in the excurrent 

 or in the incurrent passages, or in both, but it would be 

 interesting to ascertain if there is any limitation in this respect. 

 If it is in the incurrent passages that the Copepods live, they 



