November i8, 1915] 



NATURE 



325 





LR'stion whether individual chromosomes are the 

 . arers of different characters or groups of characters. 

 i he ex|>eriments of E. B. Wilson and his school on 

 Drosophila and other insects suggest that they are. 

 The best instance is the so-called sex-chromosome, 

 hich is supi)osed to carry the determiner of sex and 

 t the qualities which are sex-limited. In some cases 

 I lie female nucleus possesses one more chromosome 

 than the male, and there are two kinds of sperma- 

 tozoon, one with one more chromosome than the other. 

 n< nee it is assumed that sex is fixed by the sperma- 

 /oon. But when two species are crossed, differing 

 : a secondary sexual character, the distribution of 

 lis character in the hybrid and in the F. generation 

 lows that it cannot possibly be carried by the sex- 

 iromosome. Moreover, in other cases (Abraxas) the 

 iheritance of characters in a cross between two 

 \aricties indicates that there are two kinds of egg 

 and one kind of sperm, and yet no constant chromo- 

 somal difference between the two kinds can be detected 

 (Doncaster) ; in other words, the odd chromosome may 

 : not be the cause of sex-difference, but in itself the 

 result of that sex-difference. Prof. MacBride pointed 

 out that the phenomena of meiosis, and their agree- 

 ment in form with the sort of segregation of quali- 

 ties postulated by the Mendelian hypothesis, suggest 

 that determiners of various characters are situated in 

 definite pairs of chromatin units which become 

 separated from one another at the melotic division. 

 Since, however, the number of allelomorphic char- 

 acters can in many cases be proved to be much larger 

 than the number of chromosomes, the individual 

 chromosomes cannot represent these determiners, 

 though they may perhaps represent groups of deter- 

 miners. 



Prof. Dendy pointed out that the present controversy 

 on the subject of heredity is to a large extent a revival 

 of the old quarrel over epigenesis and preformation. 

 The preformationists are represented at the present day 

 by that large body of biologists who consider that 

 separately heritable, individual characters are repre- 

 sented in the germ-cells by definite material con- 

 stituents — determinants, "factors," etc. The pheno- 

 mena of mitosis indicate clearly the great importance 

 of the chromatin substance of the nucleus, and are in 

 complete accordance with the view that this chromatin 

 contains the invisible factors or determinants. But 

 perhaps the strongest evidence of the correctness of 

 this conception is Gates's demonstration of the correla- 

 tion between abnormal distribution of the chromo- 

 somes in the reduction division of the nucleus and the 

 phenomena of mutation as exemplified in Oenothera. 

 Prof. Dendy stated that there appeared to be no justifi- 

 cation for the assumption that the entire organism is 

 made up of separately heritable "unit characters," for 

 ontogeny is essentially an epigenetic process. After 

 referring to the influence of the environment on the 

 organism and to the dependence of progressive evolu- 

 tion on the continuance of environmental change from 

 generation to generation. Prof. Dendy directed atten- 

 tion to the great complications introduced bv the 

 sexual process, or amphimixis, whereby slightly 

 different samples of germ-plasm are mingled in ever- 

 increasing complexity from generation to generation, 

 riirough the oft-repeated process of amphimixis the 

 1 hromatin of the nucleus comes to contain a great and 

 varied collection of samples of ancestral germ-'pTasm. 

 Mendelian phenomena arc of secondary importance, 

 and result from the permutations and combinations of 

 these different samples of germ-plasm, or of the 

 so-called factors contained therein, in the process of 

 amphimixis. 



Prof. Hickson said that the evidence that the 

 chromosomes are the sole bearers of hereditarv char- 



acters is not proved, and for many reasons is not 

 probable. That the cytoplasm is the sole bearer of 

 such characters is also not proved, and is still more 

 improbable. The only proposition that is proved is 

 that thp hereditary characters are transmitted by the 

 sexual cells as a whole, and that the characters are 

 formed by the interaction of nucleoplasm and cyto- 

 plasm. He held that there is very strong evidence 

 for the belief that the act of fertilisation involves a 

 conjugation of nucleoplasm with nucleoplasm and cyto- 

 plasm with cytoplasm, and that the mixing of both 

 these plasms is essential for the process. 



Prof. M. Hartog, in referring to the statement that 

 the sperm introduced only chromoplasm into the egg, 

 pointed out that Vejdovsky had shown in the clearest 

 way in Rhynchelmis, which by the size of the plas- 

 matic elements concerned afforded the best material 

 for such study, that the middle piece of the sperm was 

 not merely a centrosome, for on entrance into the q^^ 

 it enlarges enormously into a mass of reticulate cyto- 

 plasm. This mass sends out radiating strands, which 

 feed on the yolk-granules, and so nourish the enlarg- 

 ing mass within which the centrosome is formed about 

 the centriole. 



In reply Prof. MacBride said it was true, as Prof. 

 Dendy had remarked, that the fate of a germ-cell 

 depended not only on its nature but on its environment. 

 But when the environment was altered a new type 

 was not produced, but merely a modified edition of* the 

 old type. He could not accept Prof. Hartog's view 

 that the middle piece of the spermatozoon constituted 

 an important addition to the cytoplasm of the egg, for 

 if that were so, when a cross was made between two 

 distinct species, the paternal characters should appear 

 in the earliest stage of development, which was not 

 the case. 



Material Collected in Australia or en route thereto. 



The greater portion of the meeting on the Friday 

 morning was devoted to four papers dealing with 

 material collected in or en route to Australia last year. 

 Prof. Herdman gave a short account of work by 

 himself and Mr. Andrew^ Scott on the plankton col- 

 lected during traverses of the great oceans. The 

 material was collected by letting the sea-water, which 

 is pumped continuously into the ship, flow out from 

 a bath- or other tap through a fine-meshed silk net. 

 The net was changed morning and evening, so that 

 each sample obtained represented a twelve hours' 

 catch. The amount of plankton per haul dropped 

 markedly in passing from coastal to oceanic waters. 

 Prof. Herdman referred to a number of the more 

 interesting organisms obtained. He remarked that on 

 the dav after leaving the Cape the sea was blood-red 

 in colour, and highly luminous at night. The gather- 

 ings then taken were found to contain large numbers 

 of a small red Peridlnean, which was probably the 

 cause of both the colour and the luminosity. 



Dr. J. H. Ashworth described larvee of Lingula and 

 Pelagodiscus (Discinisca), which were collected by the 

 method above-named. The seventeen larvae of Lingula 

 obtained in the southern portion of the Red Sea and 

 off Ceylon varied in diameter from 05 to i-6 mm. 

 In the smallest there was no trace of peduncle, but 

 in the largest this organ was well formed, glandular 

 at its tip, and ready to be extended to fix the animal 

 to the substratum. The shell-valves of all the speci- 

 mens were transparent, and in the case of the youngest 

 specimens were still connected together posteriorly by 

 a thin film of chitinoid substance forming a hinge. 

 The cirri, alimentary canal, statocysts, and ccelomo- 

 ducts were briefly described. Six larvae of Pelago- 

 discus were taken a few miles west of Cape Comorin, 

 and were examined alive. Thev were all about the 



NO. 2403, VOL. 96] 



