6; 



Symbiotic animals. 



As in almost every sponge numerous animals live in our Spirastrella or between its 

 processes. Thus I frequently found Annelids living in the canals and also, as we saw before, 

 an Ophiurid {Ophiactis savignyi). This is nothing remarkable; but I want to draw attention 

 to a small sort of Cirripedia. My friend Dr. P. P. C. Hoek, whom I begged to determine the 

 species, writes to me that it is "either identical with or very nearly related to Balanus declivis, 

 Darwin, which hitherto is known from the West Indus only". It seems to me probable that 

 the presence of this little Balanus is one of the causes of the club-shaped appearance of the 

 specimens infested with it, a phenomenon to be compared with the modification in shape 

 Stephanoscyphus mirabilis Allm. so often produces. The latter polyp seems also to occur in 

 Spirastrella. In sorae specimens of our sponge I found numerous cells, which I do not believe 

 to belong to the sponge but to represent symbiotic Protozoa. They strongly remind us of 

 Cnidosporidia. Unfortunately I have not been able to decide the question. 



