November 1, 1912] 



SCIENCE 



601 



flora grows at Dixie Landing with the condi- 

 tions Tinder which (E. Lamarchiana occurs at 

 its European stations. The race of CE. La- 

 marchiana which occurs at Hilversum is un- 

 mixed, since no other species of (Enothera 

 grows at that locality. Of its mutants only 

 CE. Iceviflora and (E. hrevistylis have heen ob- 

 served to flower regularly in the iield: the 

 other forms either do not flower at all or only 

 so rarely as to have hardly any influence on 

 the purity of the strain. In the sand dunes 

 of Holland, on the contrary, (E. Lamarchiana 

 is mixed, as a rule, with European (E. hiennis 

 and is observed to produce the three diiferent 

 hybrids which are obtained when these two 

 species are artificially hybridized. The same 

 statement holds good for many localities where 

 the two species grow in France and England. 

 Every individual from such a station, how- 

 ever closely its external characters may seem 

 to coincide with those of one of the parent 

 species, must always lie open to the suspicion 

 of having had a hybrid ancestry. 



In connection with the fact that the Dixie 

 Landing types are so sharply divisible into 

 two groups, it is permissible to suggest that 

 they may correspond in a general way with 

 hybrids between CE". Lamarchiana and (E. 

 hiennis " Chicago " which have already been 

 studied. From the cross CE. Lamarchiana X 

 CE. hiennis " Chicago " and its reciprocal, two 

 pairs of twin hybrids were obtained at Amster- 

 dam in the first generation, viz., CE. Iwta and 

 CE. velutina, and CE. densa and CE. laxa. The 

 first pair of twins, from the cross CE. Lamarch- 

 iana X ®- hiennis " Chicago," has already 

 been described, the other pair, from the re- 

 ciprocal cross, will soon be published in 

 :another paper. Possibly one group of the 

 Dixie Landing types is related to CE. grandi- 

 flora in the same way that CE. densa and CE. 

 Iwta are related to CE. Lamarchiana, and the 

 other group to CE. Tracyi as CE. laxa and CE. 

 velutina are related to CE. hiennis " Chicago." 

 Of course the situation at Dixie Landing is 

 probably complicated by the recrossing of the 

 hybrids with themselves and with their pa- 

 rents. However that may prove to be, the 

 Dixie Landing types are now available for 



study and it is hoped that future work may 

 show in what manner they are related. At 

 the present time no conclusion regarding them 

 is justified other than that they constitute so 

 mixed a population that it is quite impossible 

 to distinguish original parent types, if any 

 such exist there, from the derivative types as- 

 sociated with them. In case the two most 

 common types represent the original strains, the 

 presence in other types of characters which 

 are not common to either hypothetical parent 

 sxiggests that CE. grandiflora and CE. Tracyi 

 may prove to be additions to the list of species, 

 including CE. Lamarchiana, CE. cruciata 

 " Adirondack," European CE. hiennis, and CE. 

 hiennis " Chicago," which are known to be in 

 a mutable condition. 



Hugo de Veies, 



hortus botanicus, 

 Amsterdam 



H. H. Bartlett 



Bureau op Plant Industry, 

 Washington 



THE great crested GREBE AND THE IDEA OF 

 SECONDARY SEXUAL CHARACTERS 



Certain facts in the structure and habits of 

 this bird (Podiceps cristatus L.) have such a 

 general bearing upon the whole conception o£ 

 secondary sexual characters that it seems de- 

 sirable to publish them here. The facts are 

 these : the great crested grebe possesses an 

 erectile rufi at the sides of the neck and a pair 

 of erectile tufts on the head. The male is 

 slightly larger in total size, and his ruff and 

 tufts are also slightly larger, relatively as 

 well as absolutely; otherwise the sexes are 

 identical. The ruff and tufts are used exten- 

 sively in courtship; at other times they are 

 only occasionally erected, and then never to 

 their full extent. The courtship-actions, in- 

 cluding all the movements of ruff and tufts, 

 are identical in the two sexes. The ruff and 

 tufts and the actions in which they are con- 

 cerned would be called secondary sexual char- 

 acters, were they not common to both sexes, 

 for secondary sexual characters are always de- 

 fined with regard to this very point, their dif- 

 ference in the two sexes. I take a random 



