SCIENCE-GOSSIP. 



133 



there is no reason why they should be ; for his argu- 

 ments would apply equally to the ancestors of the 

 improved forms as to the unimproved. The plea 

 that these low forms will have few or no com- 

 petitors will not hold, as already pointed out ; for 

 there is no place in nature where they will not 

 have to struggle with forms in some degree higher 

 than themselves ; and, moreover, the struggle for 

 existence is generally held to be more severe 

 between individuals of a species, and between 

 closely allied species, than between more distant 

 ones. 



" Earthworms," says Mr. Wallace, " are adapted 

 to their mode of life better than they would be 

 if more highly organized." It has been already 

 shown that this argument would probably apply 

 equally to every lowly organism which exists or 

 has existed. It would, we may suppose, apply 

 equally to our Darwinian ancestor — "an animal 

 which breathed water, had a swim bladder, a great 

 swimming-tail, an imperfect skull, and undoubtedly 

 was a hermaphrodite" — which presumably was as 

 well fitted for its aqueous life as the earthworm is 

 for its terrestrial one. Eohippus, too, was probably 

 as well adapted for its marsh as the modern horse 

 is for the prairie, and showed as little probability 

 of ever developing into anything else as does its 

 supposed descendant. It may be said further, that 

 if the earthworm were to become more highly 

 , organized it. would adopt a different mode of life. 



For it is ever, according to Mr. Wallace's views, 

 some spontaneous variation in the organism which 

 lifts it on to a higher platform of existence, and to 

 which its mode of life must be adapted. 



If, then, the argument that the lower forms of 

 life remain where they are, instead of leaving their 

 low estate by means of spontaneous variations and 

 the survival of the fittest, because it would be of no 

 advantage to them to do so, be admitted, the great 

 motive power of Darwinism is lost. Further, if 

 through the countless ages of the past there has 

 been no motive power to destroy or seriously 

 modify certain lowly forms of life, where is the 

 force required to evolve new species on the hypo- 

 thesis of natural selection from other forms not 

 essentially different ? 



My conclusion, then, is that Darwinism without 

 spontaneous generation is unable to account satis- 

 factorily for the persistence of low forms of life ; 

 and that the chief argument brought forward in 

 explanation, viz., that it would be of no advantage 

 to a simple form to become more highly organized, 

 is one which if admitted puts a stop to all develop- 

 ment. 



It is a curious reflection that if Darwinism with- 

 out spontaneous generation be true, then the most 

 lowly monad that exists is the product of the same 

 forces, acting on the same material, during the same 

 countless ages, as man himself! 



29, Queen's Terrace, Jcsmond, Newcastle-on-Tyne. 



ARMATURE OF HELICOID LANDSHELLS 



AND NEW FORMS OF PLECTOPYLIS. 

 By G. K. Gude, F.Z.S. 



(Continued from page 115,) 



T)LECTOPYLIS achatina var. in/ra/asciaia (^) 



(figs. 8^a-c) is still darker than the variety 



obesa, being of a blackish or purplish-brown. Like 



that variety it is rounded in contour, but it is larger 



and more flattened ; while the umbilicus is a little 



more shallow and the peristome more flattened and 



reflexed than in the type. The peristome is livid 



purplish in colour, the left margin being paler and 



the right margin a little inflected. A whitish or 



bluish- white band below reaches from the umbilical 



angulation to the lower suture. The armature is 



similar to that of the type, but the horizontal 



parietal fold near the lower suture is visible from 



(1) Plecfopylis achatina var. infra/asciata, n. var. (figs. 84 

 a-c), differs from the type in being more rounded in contour, 

 and in the last whorl not widening at the aperture ; the 

 umbilicus is more shallow and the peristome more flattened 

 and reflexed ; the right margin is a little depressed ; the shell 

 is blackish or purplish brown above, with a white or bluish 

 white band below, reaching from the umbilical angulation to 

 the lower suture ; the peristome is purplish brown, the left 

 margin being paler. — Major diameter, 22 millimetres ; minor 

 diameter, 18 millimetres ; altitude, 8 millimetres. — Habitat, 

 Limestone Rocks, Moulmain, Burma. — Type in my collection. 



the aperture and terminates close to the ridge. 

 The specimen figured was received by me from 

 Mr. Robert Cairns. Four specimens in the 



Fig. 84.— Pkctopylis achatina var. infrafascinta. 



collection of Mr. E. L. Layard and one specimen 

 in the McAndrew collection (the latter labelled 

 •' Plectopylis refuga ") all belong to this form. The 



