ZOOLOGY AND BOTANY, MICliOSCOPY, ETC. 441 



general, proportional to the immaturity of the treated animal. He finds 

 corroboration of his views in the beautiful experiments of Baltzer on the 

 worm BonelUa. The newly-hatched larvBS are capable of becoming 

 either males or females. " If they happen to become attached to the 

 proboscis of an adult female they become males ; if they do not succeed 

 in so attaching themselves they soon settle from the water into the sand 

 or mud of the sea-bottom, and there undergo, quite slowly, further 

 development into females (almost exclusively). The plastic, reversible, 

 quantitative nature of sex in this form was show^n by this investigator in 

 the following way : Some of the free-swimming " indifferent " larvas 

 were artificially helped to a connexion with the proboscis of an adult 

 female. Some of these were permitted to maintain this attachment 

 for a very short period ; others were removed at progressively longer 

 periods, with the very significant result that practically all stages of 

 hermaphroditism were produced, those first removed becoming almost 

 perfect females, others with longer and longer periods of attachment 

 becoming more and more perfect males." 



The general idea based on the author's experiments is that sexually- 

 differentiated organisms have had, from the first, the problem of pro- 

 ducing germs pitched at two different metabolic levels. In connexion 

 therewith the germ-cells have in some cases established two different 

 chromosome complexes. But the requisite metabolic level of the germ 

 may be established in the absence of the appropriate chromosome com- 

 plex, and the sex of the offspring made to correspond with the acquired 

 grade or level of metabolism. "Most important of all, perhaps, is the 

 demonstration that one hereditary character is modifiable, is of a fluid, 

 quantitative, reversible nature. Seemingly this can only mean that other 

 hereditary characters are also modifiable." 



Reproductive Processes in Birds.*— Oscar Riddle and others have 

 made diverse studies on the reproductive processes in birds. Riddle finds 

 that when the oocyte of the fowl reaches a diameter of 6 mm. the ratio 

 of growth suddenly (within a day) increases twenty-five fold. The 

 same is observed in other birds and in reptiles. The increase is chiefly 

 in the yellow yolk, and is accompanied by changes in the growth and 

 activity of the follicular membrane. 



Adelaide A. Spohn and 0. Riddle find that in the fowl and the 

 pigeon the yolk begins to absorb water from the white as soon as it 

 leaves the ovary. The white yolk has a higher water value, is more like 

 embryonic tissue, and is in immediate contact with the embryo. 



Riddle finds that after the twelfth day of incubation the phospha- 

 tides of the yolk (20 '6 p.c.) are utilized more than the neutral fats 

 (49*5 p.c), and these faster than the protein (28*4 p.c). 



0. Riddle and A. A. Spohn find that the albumin secreted by 

 the oviducal glands at first is not an exact equivalent of that formed 

 later, differing chiefly as regards the proportion of water to solids. 



0. Riddle and Gr. C. Basset find that alcohol given by inhalation over 



* Amer. Journ. Physiol., xi. (191G) pp. 387-437. See Physiological Abstracts, 

 i. (1916)No. 9, pp. 423-4. 



