244 



HARDWICKKS SCIENCE-GOSSIP. 



of, for instance, a mammal. This is an old objection 

 to Pangenesis, and one to which Mr. Darwin replied 

 by pointing to the enormous number of molecules 

 which probably exist in a cubic millimetre of water. 

 But when we consider, first that a gemmule is very 

 much larger than even a very large molecule of a 

 complex organic substance, and secondly try to get 

 some conception of the enormous number of cells 

 which will have to be represented, the objection 

 appears of considerable force. 



The second argument I propose to consider is that 

 furnished by Mr. Francis Galton's and Professor 

 Romanes' experiments on the transfusion of blood and 

 transplantation of tissues in rabbits and guinea-pigs. 

 Mr. Galton performed extensive experiments in trans- 

 fusing the blood of distinct varieties of rabbits. He 

 obtained no hereditary effect. Mr. Darwin would not 

 admit that these experiments negatived the doctrine 

 of Pangenesis. It was no essential part of his theory, 

 he argued, that the gemmules should use the circu- 

 lation as a means of transit. Obviously they could 

 not do so in many of the lower animals and in plants. 

 But in reply we may'argue, with Professor Weismann, 

 that it is difficult to see why the gemmules should fail 

 to take advantage of so favourable a means of transit, 

 and also how they could contrive to avoid it. 

 Professor Romanes has since repeated these experi- 

 ments with great care, and has also carried out very 

 complete skin-transplantation experiments on guinea- 

 pigs of distinct varieties, again with negative results. 

 Now in this case, on the hypothesis of Pangenesis, a 

 certain number of gemmules must have been present in 

 the transplanted strips of skin, and how they failed 

 to produce any effect is not at all clear. 



Perhaps the most trenchant criticism of Pangenesis 



is Professor Weismann's, and it is best given in his 



own words. It is a criticism of Darwin's solution of 



the problem of development by the hypothesis of 



preformation. *' One and the same part of the body 



must be represented in the germ or sperm-cell by 



many groups of gemmules, each group corresponding 



to a different stage of development ; for if each part 



gives off gemmules, which ultimately produce that 



part in the offspring, it is clear that special gemmules 



must be given off for each stage in the development of 



the part, in order to reproduce that identical stage. . 



But the ontogeny of each part is in reality continuous, 



and is not composed of distinct and separate stages. 



We imagine these stages as existing in the continuous 



course of ontogeny ; for here, as in all departments of 



nature, we make artificial divisions in order to render 



possible a general conception, and to gain fixed 



points in the continuous changes of form which have, 



in reality, occurred. Just as we distinguish a sequence 



of species in the course of phylogeny although only a 



gradual transition, not traversed by sharp lines of 



demarcation, has taken place, so also we speak of the 



stages of ontogeny, although we can never point out 



where any stage ends and another begins. To 



imagine that each single stage of a part is present in 

 the germ, as a distinct group of gemmules, seems to 

 me to be a childish idea, comparable to the belief that 

 the skull of the young St. Lawrence exists at Madrid, 

 while the adult skull is to be found in Rome. We 

 are necessarily driven to such a conception if we 

 assume that the transmission of acquired characters 

 takes place."* 



These three lines of argument show the heavy 

 batteries which can be brought to bear against 

 Pangenesis from various sides. We can hardly 

 accept such a theory unless no other is possible. 



Various attempts at modifying it have been made, 

 of which, perhaps, the most important is Mr. W. K. 

 Brooks'. t I shall not, however, discuss it here, but 

 refer the reader who is interested in the matter to 

 Professor Weismann's very complete criticism of it 

 (" Essays on Heredity" pp. 326-332). 



{To be continued.) 



ROSSENDALE RHIZOPODS. 

 No. 6. 



ALL the Rhizopods figured and described in my 

 previous articles, have belonged to the sub- 

 order Lobosa — having lobose, or finger-like pseudo- 

 podia, and containing many forms familiar to most 

 microscopists. I have now to describe some less 

 familiar Rhizopods, belonging to the sub-order 

 Filosa. In this sub-order, the sarcode is not so 

 obviously separable into a clear ectosarc and a more 

 granular endosarc, but apparently consists wholly of 

 the latter ; and probably on this account the pseudo- 

 podia, instead of being lobate or finger-like, are in 

 the form of exceedingly delicate, forked threads, 

 which become finer and finer as they branch, and 

 are usually more numerous than those of the lobose 

 Rhizopods. The sub-order contains seven genera, 

 five of which are represented in this district, and 

 about seventeen species, some of which are beautiful 

 objects, the tests being made up of round, or oval, 

 ovai--lapping plates, arranged in such a way as to 

 form definite patterns. 



Famphagus muiabilis, perhaps the most interesting 

 species of the genus, I have not yet met with ; but 

 another species, F. hyalinus, is not uncommon in our 

 clear ponds and wells, though from its minuteness 

 and inconspicuous character, it may readily be over- 

 looked. On a side view it is sub-spherical, and the 

 lower end is produced into a short neck, with a cir- 

 cular mouth, through which the long, fine pseudo- 

 podia are protruded. As generally seen, it appears 

 as a roundish granular mass, greyish in colour, 

 occasionally with cloudy yellow patches in the 

 interior, and in specimens from some localities 



* " Essays on Heredity," pp. 316-317. 

 t "Law of Heredity," 1883. 



