September ■i, 1908] 



SCIENCE 



317 



legless and sei-pentiform in shape. In the 

 absence of the skull, he referred the form, as 

 Cope had done, to the Eeptilia. Two years 

 later F. Broili thought that he recognized in 

 some imperfect skull material of the same 

 species a pair of fiat bones below the palatal 

 region, which he believed to be gular plates. 

 As such plates are characteristic of fishes and 

 unknown in reptiles, with which he also 

 classed the genus, he reached the rather start- 

 ling conclusion that the reptiles were, in part 

 at least, derived directly from the fishes — a 

 conclusion, it is needless to say, which was 

 received with doubt and incredulity by 

 naturalists. Because of this extraordinary 

 character he proposed for the form the family 

 name Paterosauridse. 



Recently, in the examination of the Texas 

 Permian material in the Chicago University 

 collection, I was so fortunate to find a skull 

 of Lysorophus in connection with vertebrse, 

 which, upon preparation proves to be wonder- 

 fully perfect and complete. The so-called 

 " giilar plates " of Broili are merely and 

 clearly four pairs of epibranchials, all nearly 

 of the same size, the first pair only with 

 a stout pair of ceratobranchials connected 

 with them. Upon the whole the branchial 

 apparatus resembles not a little that of 

 Necturus or Proteus; and indeed there are 

 certain other resemblances to these sala- 

 manders in the skull that can not be over- 

 looked — the small, pointed snout, the very 

 small size and anterior position of the orbits 

 and nares, especially. The temporal region is 

 unossified; the basioccipital is ossified and 

 there are two occipital condyles. There is no 

 pineal eye ; and there is a pair of large plates, 

 apparently proatlantal, back of the small, un- 

 paired supraoccipital. 



Lysorophus was a slender, well-ribbed, ser- 

 pentiform, legless, probably blind, mud-bur- 

 rowing amphibian, with long, one-headed ribs 

 attached neurocentrally, and with notochordal 

 vertebra, strangely resembling, though genet- 

 ically very distinct from, the modern Csecilia. 

 In skull structure it is not unlike modern 

 amphibians, but will doubtless require the 

 erection of a new group for its reception, a 



group equivalent to the modern Caecilia. In 

 length the creature may have reached a foot 

 or fifteen inches, though the skuU measures 

 but a trifle more than half an inch. 



S. W. WiLLISTON 



University of Chicago 



COMBINATIONS OF ALTERNATIVE AND BLENDING 

 INHERITANCE 



Whether blending and alternative inherit- 

 ance are fundamentally the same thing or not, 

 they are usually sharply to be distinguished 

 in their end results. Mendelian work has 

 been almost wholly concerned with alternative 

 inheritance. However, usually each member 

 of the Mendelian pair exhibits fluctuating 

 variation. Tallness of peas is dominant in a 

 Mendelian sense over dwarfness, but each sort 

 varies as to height. When either condition is 

 pure (homozygous) only blending inheritance 

 is concerned. When the two conditions are 

 crossed we have to consider a combination of 

 both alternative and blending inheritance. 



When the ranges of variation of the two 

 conditions do not overlap no confusion would 

 occur. However, when they do, although 

 Mendelian segregation and purity of germ 

 may be as perfect as ever, confusion would 

 arise. In the beetle Crioceris asparagi there 

 are three pigmentless areas on each elytron. 

 These areas may be distinct or they may be 

 united in various degrees. Usually it is the 

 anterior and middle area which unite. They 

 may be well united, or only faintly so, or not 

 united at all but extra large, or they may not 

 be united and small. It seems' that the con- 

 dition of areas-distinct-and-small is a Men- 

 delian dominant over areas-united. However, 

 the recessive character is subject to the 

 fluctuation just mentioned and the inheritance 

 of these fluctuations is a problem of blending 

 inheritance as contrasted with the problem of 

 areas-distinct vs. areas-united. 



I have been carrying on a study of the in- 

 heritance of abnormal venation in Drosophila 

 ampelopMla for about forty generations of the 

 fly. As was pointed out in a preliminary 

 report of the work before the Boston meeting 

 ' Lutz, Psyche, June, 1908. 



