118 



DUDLEY MEMORIAL VOLUME 



Atlantic Coast 

 Lutianus cyanopterus 

 Lutianus apodus 

 Lutianus analis 

 Lutianus synagris 

 Hcemulon album 

 Hamulon parra 

 Hosmulon schrancki 

 Anisotremus surinamensis 

 Anisotremus virginicus 

 Conodon nobilis 

 Pomadasis crocro 

 Calamus macrops 

 Xystoema cinereum 

 Eucinostomus pseudogula 

 Kyphosus incisor 

 Isopisthus parvipinnis 

 Nebris microps 

 Larimus fasciatus 

 Odontoscion dentex 

 Corvula sialis 

 Bairdiella vera-crucis 

 Micropogon furnieri 

 Umbrina broussoneti 

 Menticirrhus littoralis 

 Eques acuminatus 



Pacific Coast 

 Lutianus novemfasciatus 

 Lutianus argentiventris 

 Lutianus Colorado 

 Lutianus guttatus 

 Hcemulon sexfasciatum 

 Hcemulon scudderi 

 Hcemulon steindachneri 

 Anisotremus interruptus 

 Anisotremus toeniatus 

 Conodon serrifer 

 Pomadasis branicki 

 Calamus taurinus 

 Xystcema simillimum 

 Eucinostomus dowi 

 Kyphosus analogus 

 Isopisthus remifer 

 Nebris zestus 

 Larimus pacificus 

 Odontoscion xanthops 

 Corvula macrops 

 Bairdiella armata 

 Micropogon ectenes 

 Umbrina xanti 

 Menticirrhus elongatus 

 Eques viola 



This list may be greatly extended, but the series noted will illustrate the 

 point in question. Whenever a distinct and sharply defined barrier exists, 

 geminate or twin species may be found on the two sides of it, unless, as some- 

 times happens, the species has failed to maintain itself on one side or the 

 other of the barrier. So far as Panama is concerned, we have evidence 

 that the barrier was raised near the end of Miocene time with no trace of 

 subsequent depression. We can thus form some estimate of the age of 

 separation in at least a small number of closely related species. In this and 

 similar cases it is not possible to conceive of the formation of these species 

 by sudden mutation, or that they would retain their separate existence were 

 the element of segregation removed. While segregation or isolation is not a 

 force, and perhaps not strictly a cause in species formation, it is a factor 

 which apparently can never be absent, if the species retains its independent 

 existence. 



There is no doubt that the distribution of higher animals in general is in 

 accord with "Jordan's law.'' Examples by the thousand come up from every 

 hand. If we had a hundredth part of the amount of available evidence in 

 support of mutation theories, these theories would pass from the realm of 



