AND OTHER MEUITERRANEAIS" LOCALITIES. H 



Prom Eapallo I have the plumosa form with the small cap-like 

 ovicell of the variety aperta of Hiacks, and it occurs on both 

 the forms from Trieste ; but from analogy with other Bryozoa it 

 would seem possible that the remarkably small ovicell may be a 

 stage of growth ; that is to say, the ovicells are only in the initial 

 stage. We may in colonies of Bryozoa find the ovicells in every 

 stage of growth ; on the other hand, this is not always the case, 

 for I have specimens of Retepora in which most zooecia show 

 the small semicircular plate, indicating the commencement of the 

 ovicell, though none have complete ovicells. 



If more abundant material should show that I am wrong in 

 the interpretation of these points, then we have B. spicata var, 

 aperta, B. spicata, B. plumosa var. aperta, and B. plumosa — all 

 living side by side ; but if these are to be specifically separated, 

 it must be upon other distinctions than those at present 

 indicated. 



The primary zooecium has a central spine at the base of the 

 area*, and on each side two spines near the distal end. It is not 

 only the first zooecium which may possess ancestral characters, 

 but two, three, or even more uniserially arranged may have the 

 same shape before the normal zooecia are formed ; and in this 

 species there are sometimes near the base a number of zooecia 

 longer than the normal ones, but with the area very short. The 

 repetition of the ancestral characters in the few first zooecia we 

 may see in B. avicularia, B. calathus, and B. neritina ; and 

 further, in B. jylumosa from a single zooecium zooecia may spring 

 out at each side and form new branches, but this does not t>eem 

 to be a common method of increase. 



Another mode of increase is of great interest, and was found 

 in colonies growing in the aquarium of the Zoological Station in 

 Trieste — some basal zooecia producing either direct (PI. 2. fig. 7), 

 or from lateral zooecia (fig. 6), long processes which seem scarcely 

 to diff'er from the radicals, or attachment fibres, except in being 

 rather stouter. These processes may equal ten zooecia in length, 

 and at the end a young polypide buds, and in some cases from 



* I term this " area," for " aperture " seems eminently unsatisfactory seeing 

 that there is no aperture, but only a thinner portion of the front wall. It 

 might perhaps be better to term it " opesium," but at present a general term 

 may be safer. " Aperture " is probably a relic from times when only dried 

 specimens were examined and low powers used, and a real aperture was thought 

 to exist. 



