228 



HARDWICKE'S SCIENCE-GOSSIP. 



[Oct. 1, 1870. 



pellation for Ranunculus arvenm, a very common 

 weed on all strong soils in Shropshire, and whose 

 comb -like achenium quite explains the term 

 " currycomb." Why it should be delivered up to 

 Satan, I do not know, unless its extremely acrid 

 properties have led to its association with the infer- 

 nal power. Beggar's needle is Scandix Pecten 

 Veneris, and is a name frequently given to the plant 

 in other countries beside this. The Knot-grass 

 {Polygonum aviculare) is the pest of light soils 

 hereabouts. It comes up and grows with wheat 

 and barley, and when these are cut covers the 

 stubble. Some farmers say clover seed is adulterated 

 with the seed of this plant, and thence its profusion, 

 particularly upon barley stubble clovered down. 

 It is known to labourer and farmer alike by the 

 name of " pig-grass," but why, I cannot discover. 

 That clover seed is largely adulterated there is no 

 doubt. I once saw a large crop of Sherardia 

 arvensis, with here and there a root of clover. The 

 Sherardia might have been regularly cut with a 

 scythe, and its regular growth iu the drills left no 

 shadow of a doubt of its having been sown. 

 Wellington, Salop. Robert Akslow. 



PLUMATELLA BEPENS. 



LAST August I obtained from a pond at Penge 

 a quantity of that beautiful freshwater poly- 

 zoon, Plumatella repens, where, I may mention, 

 they were growing thickly in masses, sometimes 

 of considerable size, on every weed and stick. I 

 brought some pieces away with me, and placed them 

 in a pond in this neighbourhood (Sheerness), where 

 I had the satisfaction, the other day, to find they had 

 become naturalized in their new abode. 



I have derived so much pleasure from observing 

 these beautiful objects, that I am induced to think 

 a few words on the subject may interest such of your 

 readers as may not be already quite familiar with 

 them, and have called the pencil to my aid to give, 

 so far as can be done, some idea of their appearance. 

 They belong to the molluscous division of animated 

 nature, of which, with the Tunicata, they form the 

 lowest subdivision, being called Bryozoa on ac- 

 count of their mossy appearance when viewed in 

 clusters. They have a superficial resemblance to 

 many forms of marine polypes, as Sertularia, Lao- 

 mecka, &c., from which, however, they are widely 

 distinguished by the possession of an anal orifice, 

 and the presence of striated muscular fibre. In 

 fig. 190 I have shown a colony of these creatures 

 attached to a stem of water crow-foot, and exhi- 

 biting various appearances, according to the aspect 

 in which they are viewed, as seen with a pocket 

 lens. Fig. 19S shows a single individual enlarged, 

 viewed with an inch glass : a is the crown of ten- 

 tacles, b the exterior and transparent covering 



thrown off by the inner and living sac, c, from which 

 the tentacles are protruded by a process of eversiou 

 similar to the turning inside out of a stocking. 

 The stomach-cavity, d, is surrounded by thick walls 

 of great contractility, whereby a continual move- 

 ment of the contents is kept up, the food being 

 alternately driven up and down the stomach, at the 

 lower end of which I think I have sometimes 

 detected a very delicate inner lining, which seemed 



Fig. lgG. Group of Plumatella. 



to prevent the dark-coloured mass of food from 

 completely reaching the bottom in its downward 

 course : e is the intestine, having its anal orifice at 

 /, close under the base of the disc of tentacles; and 

 from this orifice masses of excrement itious matter 

 are occasionally seen to pass and float away in the sur- 

 rounding water. The disc from which the tentacles 

 proceed is called the Lophophore, or crest-bearer, 

 and I have made it the subject of a separate drawing 

 uuder a half-iuch glass (fig. 197). It is of a deeply 

 crescentic, or rather horseshoe shape, as is most 



