POLYCYSTINS. 



PREFACE 



"But WHA.T ARE PoLYCYSTiNS " is the constant exclamation. — So little is yet known of these 

 curious organisms that Naturalists have not yet decided on their exact place. They belong 

 however, to the sub-kingdom "Protozoa," and Mr. Reay Greene in his "Manual" places 

 them between " Rhizopoda " (of which the type is Amoeba, so commonly found in fresh water 

 as little gelatinous lumps, of the very lowest form of animal life) and Sponges, which form 

 flinty interior skeletons, called Spicules, to support the Spongiose web, and the animal mass 

 of jelly, called Sarcode, with which they are invested. The Fohjcystias are also masses of 

 Sarcode, but they appear to form both internal spicular-like supports radiating from the 

 Nucleus, and also external shells of a network of flint, through the insterstices of which they 

 are said to protrude Pseudopodian threads (perhaps analogous to the Tentacles of Sea-anemones 

 and Star-fishes or arms of Hydra) by means of which they are supposed to imbibe noiu'ishment, 

 and to have some powers of locomotion. A careful observation of the larv4l changes of the 

 Echinoderms, and the Pupae states of other young things, can make one understand how the 

 protean forms of the Polycystins need not all designate distinct species, but that many grotesque 

 diff'erences of shape, and of spinous ornamentation may, in reality belong to the same object, 

 in different stages or under different circumstances of development, such as more or less pressure, 

 abundance or scarcity qf the siliceous material in the surrounding water, &c. Perhaps there may 

 be said to be four classes of form : — 1st., the discoidal or planorbian flattened spheres, variously 

 winged or bordered ; 2nd., the Orbicular, with or without spines ; 3rd., the vase or bellshaped, 

 consisting often of repeated globes growing out of each other, sometimes with a re- duplication 

 of parts, that might seem to indicate a tendency towards increase by fission ; 4ith., the plane 

 or straight-sided forms. 



Dr. Wallich promises a full history of the structure and mode of development of Polycystins 

 in his forthcoming work, having obtained living specimens in his recent deep-sea soundings : 

 some in association with those wondrous benighted star-fishes from two miles deep. 



Professor Johannes Miiller fished them up frequently in the Mediterranean, near Cette and 

 St. Tropez; always from great depths, and under very clear pure sea water, but from their 



