1899] IS TELEGONY A MARES NEST? n 



which almost exactly resembled its dam. In other cases similar 

 negative results were obtained, any remarkable peculiarities that oc- 

 curred being interpretable rather as reversions provoked by hybridism, 

 than as furnishing any evidence of telegony. 



In a paper on " Reversion in Birds and Mammals," read before the 

 Royal Society of Edinburgh on December 5 th, of which no adequate 

 report has yet reached us, Professor Ewart summed up the results of a 

 long series of experiments in crossing. He showed that reversion does 

 not invariably follow crossing ; thus the offspring of Galloway and 

 Highland breeds of cattle might be indistinguishable from pure-bred 

 Galloways, while a cross between a pure white fantail pigeon and a blue 

 pigeon resulted in an intermediate form, with the colour of the fantail 

 and the build of the pouter. On the other hand, he showed that 

 crossing is often followed by reversion, as in the case of a cross between 

 an Archangel and a White Fantail, which resulted in a bird exceedingly 

 like a Blue Rock. But we wait impatiently for something better 

 than a newspaper report of these experiments, which are as important 

 as they are interesting. 



A Study in Hybridism. 



It is a far cry from horses to sea-urchins, but the phenomena of 

 hybridism in the two sets of cases seem to be in some respects very 

 similar. In his paper on " The Relations between the Hybrid and 

 Parent Forms of Echinoid Larvae " {Phil. Trans. Series B, vol. cxc. 

 (1898), pp. 465-529), Mr. H. M. Vernon shows that various species — 

 Strongylocentrotus lividus, Sphacrcchinus granularis, and Echinus micro- 

 tuberculatus — are not separated by any rigidly-fixed physiological 

 barrier. In fact, there is a general capacity for hybrid-fertilisation. 

 In one case (viz. Echinus ? —Strongylocentrotus (?) cross -fertilisation 

 takes place with greater ease, and produces larvae of larger size than 

 does direct fertilisation. 



In most cases the larvae are of the maternal type, but paternal and 

 intermediate types also occurred. But the most interesting result is 

 the evidence of a connection between the relative maturity of the 

 germ-cells and the characteristics which find expression in the hybrid 

 larvae. "The Strongylocentrotus" ^ — Sphaerechinus 6 hybrid is only 

 formed at the time when the Strongylocentrotus ova have reached their 

 minimum of maturity ; whilst in the case of the reciprocal hybrid it 

 is shown that as the maturity of the Strongylocentrotus sperm increases, 

 it is able to transmute first a portion and then the whole of the hybrid 

 larva from the Sphacrcchinus to its own type. In other words, the 

 characteristics of the hybrid offspring depend directly on the relative 

 degrees of maturity of the sexual products." It seems as if we might, 

 through such admirable researches as Mr. Vernon's, be able some day to 

 invest with some reality the subtle conception of intra-germinal struggle. 



