365 



POLTCISTINA OF BARBADOS. 

 By the Rev. J. E. Vize, M.A., F.R.M.S., &c. 



I MOST commence by a short apology for the introduction of this subject-so 

 foreign to the stu.lv of mycology or even botany in any shape It >s nUroduced 

 because Dr. Bull has e.xpressed a desire for it, and upon the grounds of the 

 Woolhope Club not being sectional, or in any ways limited in >ts scope of 



'"^^The Polycistina are very beautiful and very various in shape. They have 

 been found more abundantly in the Island of Barbados than any where else, where 

 they existed formerly in very vast numbers, so much so that their skeletons have 

 formed a considerable amount of rockwork. I was told some time since that their 

 numbers were very much reduced, and consequently the possession of the original 



material is valuable. , , t^ ,. j i 



They are singular creatures, for fortunately, old though the Barbados rocks 

 are, they have living representatives in the Mediterranean. From them therefore 

 we learn their life history, and to a certain extent their classification. They are 

 creatures of low animal life, furnished with skeletons, it is said, of sUica of 

 wondrous beauty and variety as to shape. As to this silica I may refer again 



^'Thfskeletons are perforated with holes of various shapes, and have been 

 formed of web-like deposits which the living Polycistin has woven for itself 

 external to its body which is really sarcode. This sarcode has projections which 

 it protrudes through the perforations ; they are pseudo-podia, and are most usefu 

 not only for motion from place to place, but also for collecting food of the minutest 

 kind such as diatoviaceo^, small microscopic forms of alg^, sponges, &c., which 

 they'draw inside them, retaining the nutritive part and rejecting the remainder. 



They are different to the diatoTiiacect, desmidiei, and other microscopical forms 

 in one respect, namely, that they are very variable in their growth, in this respect 

 resembling Agaricus melleus. So irregular are they, that it would scarcely be 

 unfair to call species of the same kind polymorphous. 



This is one reason which I cannot think they are siliceous. Take the skeletons 

 of diatoms and desmids, you find them very constant as to size, shape, &c.. so 

 much so that one often wonders how it is that you never find them varying 

 Desmids seem all to be born, as it were, on the same birthday, and to a tain full 

 size, colour, and perfection the very time of birth. They are wonderful m th.s 

 respect, and are silica because indestructible in nitric acid. 



Now Polycistina are destroyed at once in nitric acid. An old and much 

 valued friend of mine, the Rev. T. Furlong, of Bath, was the first to discover t^e 

 way by which the Polycistina were separable one from the other. He told me 

 how he managed to do them, and also communicated to the Bath Microscopical 



