100 



SCIENCE-GOSSIP. 



r>lAY 1, 1865. 



A POPULAR DESCRIPTION OE 

 POLYCYSTINS. 



By Mks. p. S. Bury. 



[7HILST engaged ml861 and 1862 in deline- 

 ating the microscopic forms in some of the 

 Barbadoes earths brought to England by Dr. Davy, 

 and beautifully prepared for the microscope by Mr. 

 Johnson, of Lancaster, the progress of my interest- 

 ing occupiitiou being partially watched by the late 



Fig. 64.— STErnANASTRtTM, Ehr, 



accomplished Dr. Boott, he exclaimed, "You surely 

 have found the excavated toilette-service of Titania, 

 with all her essence-bottles and trinkets." Yes, in 

 that dirty-looking, chalky earth are indeed found 

 exquisitely jewelled vases, and diamond crosses and 

 stars, to represent in fairy miniature the badges of 

 every order of knighthood. But what, then, are these 

 Polycystins ? They are a family of the Eltizopods; 

 the tijpe of which group, and the object most attain- 

 able for examination, is the amoeba, which may so 

 frequently be found in the sediment of fresh-water 

 streams or pools, or even in the moss of damp 

 garden-walks, or similar situations, like drops of a 

 translucent jelly, each drop having within it, though 

 only discernible to practised microscopic eyes, a 

 speck, an atom, which physiologists term the nucleus, 

 and suppose it to be the first germ or commence- 

 ment of animal life in its lowest form. The enve- 

 loping jelly is called sarcode, and differs but slightly 

 from the cellulose of low vegetable forms of life. 

 The little lump or globule of sarcode is self-coherent, 

 though it is supposed to have no outer skin or inte- 

 gument to hold it together ; and if watched under a 

 lens, it will be seen to shoot out small portions like 

 fingers, or as they iU'e called pseudopodla (false feet). 



with which it has the power of creeping along in its 

 native clement; nay, more wonderful still, it can 

 seize with them any small infusoria or alga, fre- 

 quently some small diatom, which it can completely 

 suck into, and bury in its own substance, melting 

 out, as it were, all the nutritious part for its own 

 sustenance, and then throwing the useless debris to 

 the outside of the mass of sarcode. " Here, then, 

 we have,"— as Dr. W. B, Carpenter so eloquently 

 expresses it, — "living substances in which vital 

 operations are carried on without any special instru- 

 ments whatever; a little particle of apparently 

 homogeneous jelly, changing itself into a greater 

 variety of forms than the fabled Proteus, laying hold 

 of its food without members, swallowing it without 

 a mouth, digesting it without a stomach, appro- 

 priating its nutritious material without absorbent 

 vessels or a circulating system, moving from place 

 to place without muscles, feeling (if it has any power 

 to do so) without nerves ; and not only this, but in 

 many instances forming shelly coverings of a sym- 

 metry and complexity not surpassed by those of any 

 testaceous animals." 



Now, the Polycystins are lumps of sarcode; and it 

 is precisely this power of constructing shelly cover- 

 ings which attracts our notice to them. They ac- 

 tually do spin or weave for themselves coverings 

 resembling the most delicate and costly silver fila- 

 gree-work, rivalling in pattern the choicest pro- 

 ductions of the ancient Peruvians or modern 

 Easterns. Yet, our little Polycystin artificers choose 

 a far more beautiful material than silver, being a 

 shining transparent preparation of silex, which these 

 little lumps of apparently inert jelly possess, — a cun- 

 ning laboratory capable of extracting the silex from 

 tlic sea-water and fitting it for use. But it is not 

 only outer-corselets that they construct, there are 

 also solid internal pillars and rafters to support and 

 strengthen the fabric, in the exterior walls of which 

 suitable and convenient open spaces are carefully 

 left for the extrusion of the pseudopodia, which we 

 may suppose are sent out in all directions to collect 

 and bring home whatever is needful, either for 

 nourishment or for continuing their work. The 

 internal supports so much resemble the nature of 

 the spieulce of sponges, as to bring the polycystins 

 and sponges into very near relationship, although 

 they belong to distinct groups of the family of 

 Bhizopods. As yet so few naturalists have observed 

 the Polycystins in a living state, that their history 

 seems hardly determined. Dr. Wallich has in store 

 amass of valuable information, which he has not yet 

 given to the public. Among the most diligent, careful, 

 and successful observers of these organisms was the 

 late Professor Johannes Miiller, who fished them up 

 in quantities from their native habitats on the sea- 

 bed, under the clearest and pui-est sea-water of the 

 Mediterranean, near St. Tropez and Cette. But 



