VISIBLE AND INVISIBLE CHARACTERS IN SILKWORMS. 



141 



One of the advantages gained by the nocturnal feeding of 

 worms is that the leaf can be gathered at sundown, and so keeps 

 fresher, and does not fade as readily as when plucked in the 

 morning. There is also very little chance of attacks from the 

 dreaded silkworm fly, which is always on the alert during the 

 brightest and hottest hours of the day. 



I have found that the leaf from male trees of Morns Indica 

 gives better results in feeding silkworms than that of the female 

 trees. The dioecious character of the mulberry is not, as far as I 

 know, known to sericulturists, for in most handbooks on the 

 subject they advise rearers to select trees which bear little or no 

 fruit. The inconspicuousness of the catkins and pseudo-spikes of 

 the mulberry has evidently led to the difference between the 

 trees being overlooked by all but botanists. As the flowers are 

 inconspicuous they are anemophilous, and the trees, when in 

 flower in February, may be seen giving off pollen in little puffs 

 like smoke. This is best observed w r hen there is no breeze. 



Additional Observations made during Experiments. 



The inheritance of the visible colour character of the cocoons is 

 clearly Mendelian. 



The parent cocoons of the Ital.-Jap. Hyb. were of the yellow 

 Italian $ and white Japanese $ . 



The colour of the yellow Italian cocoon is of a deep pinkish 

 yellow {carneo-giallo or flesh colour), which sometimes varies from 

 a deep orange to almost white, but never of the vivid yellow of 

 the Indian cocoon. All the cocoons of F T of this hybrid were of 

 a pale flesh colour, none were white like that of the Japanese 

 parent. A character which dominates after a cross is made was 

 described by Mendel as dominant, and the character which 

 seemed to have disappeared he called recessive. So the flesh 

 colour of a cocoon is a dominant character, and the white 

 a recessive. All observed results in the study of heredity point 

 to the dominance of a character being due to the presence of that 

 character, and the recessive to the absence of the dominant 

 character. 



The flesh colour of the Italian is due to the presence of the 

 flesh colour and to the absence of the vivid yellow colour of the 

 Nistri. While the white colour of the Japanese cocoon is due to 

 the absence of both the pinkish yellow and bright yellow colours 

 — the example of the inheritance of eye-colour in man might 

 make this clearer. Here the dominance of brown eyes can he 

 traced to the presence of a brown pigment ; and the recessiveness of 

 blue eyes to the absence of the brown pigment. All human eyes 

 (except those of Albinos) have a layer of deep purple pigment on 

 the inner surface of the iris, but in brown, hazel, green, and grey 

 eyes there is also a layer of brown on the outer surface of the iris, 

 and it is this brown layer which entirely (if abundant) or partly 

 conceals the purple layer. In clear grey and clear deep and pale 



