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AaBb AaBbCc agouti factor albino allelomorphic pairs average bison bone bred breed true breeding test Cavia aperea Cavia porcellus cavy cent characters class of matings coat coefficients of variability color factor condition dark dilute epididymis epistatic equal numbers experiments female hybrids females with guinea-pig fertile females fertile hybrid males gametes gave growth curves guinea guinea-pig females guinea-pig males hair heterozygous in agouti homozygous hybrid animals incompletely dominant infraorbital foramen inheritance light-bellied litters male guinea-pigs mated inter matings recorded measurements Mendelian microscopic test motile sperm non-agouti obtained offspring parent species pig males pigmentation probable expectation produced pure wild race ratio recessive rough segregation skeletal dimensions skull smaller smooth species crosses spermatozoa sterile sterile males suture ticked belly total number TV wild W. E. Castle wild agouti wild females wild Guinea-pig wild hybrid wild i wild wild males young zygotic classes zygotic formula zygous
Page 102 - It appears, therefore, that hybridizing alters the sex ratio by producing a marked increase in the relative proportion of males. This conclusion is in essential agreement with that reached by Buff on, by R. and M. Pearl, and by Guyer." King found 231 males to 194 females in the totals of the first three hybrid generations, this being a ratio of 119.07 males to 100 females. Minot (1891) crossed guinea-pigs inter se and obtained 223 males to 187 females, or a ratio of 119.2 males to 100 females.
Page 82 - ... of an extended genetic study. Much of the literature deals with the subject of sterility from a taxonomic point of view, for the fertility or sterility of the hybrids is considered a criterion of the close or distant relationship between the parents. From time to time compilers have given lists of species crosses with brief mention of the partial or complete dominance of one parent and the fertility of the hybrids when known. As in most other genetic studies, the botanists have led the way, and...
Page 51 - FI generation, the more variable F2 generation, the recovery of parental types, and the tendency for certain recombinations to breed true while others split up again. There is a small number of cases of size-inheritance in which a Mendelian explanation seems well justified.
Page 102 - ... fact, the few female pheasant hybrids that I have been able to find in museums are not similar in appearance nor do they resemble the males. As hybrids they are as interesting in every way as the males and it seems probable, therefore, that had there been more of them they would have been preserved. When due allowance is made for all errors the facts still indicate that there is a marked tendency for hybrids, especially those from widely separated parents, to be male.
Page 79 - Harvard University Sterility is a common phenomenon in the hybrids obtained by mating members of distantly related groups or types, both in animals and in plants. In fact, there is a' tacit understanding among the taxonomists that members of the same species produce fertile offspring when mated inter se; but a successful cross between members of different species or genera may result in sterility of one or both sexes among the hybrids. In case both sexes are sterile, a further genetic study becomes...
Page 92 - There are further reasons for concluding that the motile spenn of the hybrid males may be physiologically different from those of the normal guinea-pig, for it often required much more time to obtain young from the hybrid males and the litters -were unexpectedly small. It may be added that sterility was not due to the absence of secondary sexual characters...