摘要:

Homologous chromosomes in the Diptera associate side by side in pairs at each and every anaphase (somatic pairing) and reappear in the following prophases relationally coiled. In plants and animals other than Diptera the homologues at anaphase (with one exception) show no such specific attraction: at prophase the relational coiling of homologues is here supplanted by a relational coiling of sister chromatids. The one exception arises at the anaphase of the last premeiotic division—homologues become associated in pairs and reappear in the following prophase relationally coiled.In the Diptera the chromosomes are single at each and every anaphase: in other animals and plants the chromosomes are double at all anaphases except that of the last premeiotic division. Hence at this latter division the attraction in pairs between chromatids is replaced by an attraction between pairs of homologues.

ISSN:1923-4287    

DOI:10.1139/cjr42d-018

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

Vitamin C analyses on canned chicken indicate an appreciable amount in the product manufactured by improved methods. This amount, while low in proportion to that found in other foods, is sufficient to indicate the conservation of the vitamin by processes that minimize exposure to oxidation. The possible application of vitamin C analyses as an objective correlate to quality conservation in canning is discussed.

ISSN:1923-4287    

DOI:10.1139/cjr42d-019

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

The distribution among maize plants of the eggs of the American boll-worm,Heliothis armigeraHb., is discussed and analysed.The problem is considered in relation lo what is known of the connection between the state of development of maize plants and their attractiveness to ovipositing boll-worm moths. The actual frequency distribution of the eggs suggests a random as opposed to a uniform distribution, but it is shown that the conditions required for a pure mathematical random distribution cannot be satisfied. Because the maize plants differ from one another in absolute degree of attractiveness at any one time, and in relative degree of attractiveness with the passing of time, it is not true that every plant has the same chance of receiving any given egg.It is demonstrated that a mathematical theory, which is eventually one of random distribution, but which incorporates a modification to allow for the varying degrees of attractiveness of the plants, gives a fairly good representation of the egg distribution found in the field.Theoretical distributions to fit the data are calculated by two methods. One is a discontinuous process which is presented as only a rough approximation of what it is intended lo express. The other uses the compound Poisson series of Greenwood and Yule. The continuous variation in nature both in space and time, which is the essential difficulty of the problem, is discussed.

ISSN:1923-4287    

DOI:10.1139/cjr42d-020

出版商:NRC Research Press    

年代:1942

数据来源: NRC