334 SECTIONAL TRANSACTIONS.— D. 



It is important to determine the class of physical phenomena to which amoeboid 

 movement belongs. Crude analogies suggested that a moving amoeba was compar- 

 able with a fluid drop in which the surface tension is lowered at one point. Micro- 

 dissection and other evidence show this view to be untenable, and that movement 

 is associated with the ready changes of state of the protoplasm from a fluid ' sol ' to 

 a contractile, solid ' gel ' and vice versa. 



These changes are most easily observed in the ' Limax ' type of amoeba, in which 

 it can be seen that each particle of protoplasm undergoes a more or less rhythmic 

 change of state, sol=gel. 



A physiological study of the amoeba shows that in the effect of temperature and 

 of salts there is abundant evidence that the mechanism of movement is identical 

 with that in the contracting muscle fibre. 



During the course of evolution it seems that fundamental physiological systems 

 such as the processes involved in contractility have remained unchanged, although 

 the structures in which contractility occurs have undergone great morphological 

 changes. 



Afternoon Meeting in the Department of Textile Industries in the 

 University of Leeds. Exhibit and papers by Dr. P. W. Dry and 

 Prof. A. F. Barker. ^See p. 414.) 



Monday, September 5. 



Dr. A. J. Grove, — The Passage of the Spermatozoa into the Cocoon in the 

 Brandling Worm, Eisenia fcetida (Sav.). 



In the account which has been given of the process of cocoori deposition in this 

 worm it was shown that the eggs pass back from the apertures of the oviducts to the 

 cocoon while the latter is still surrounding the clitellum, but it could not be determined 

 at that time how the spermatozoa entered. 



In sections through the albumen of cocoons fixed some short time after deposition, 

 spermatozoa are found lying in varying positions indicative of a condition of inactivity 

 following upon failure to enter an egg. In the albumen of cocoons dissected from 

 around the clitellum just prior to deposition no spermatozoa could be detected. In 

 freshly deposited cocoons spermatozoa are to be found surrounding the eggs but not 

 actually penetrating the vitelline membrane. The outline of these spermatozoa is 

 sinuous, indicating that they were actively swimming at the time of killing. 



The evidence obtained supports the view that, although the eggs are passed back 

 into the cocoon while the latter is still surrounding the clitellum, the spermatozoa 

 enter during the passage of the cocoon over the apertures of the spermathecse. This 

 difference in the method by which the two reproductive elements enter the cocoon 

 is associated with the posterior position of the clitellum so characteristic of the 

 Lumbricidos. 



Mr. Arthur M. Banta and Mr. L. A. Brown. — Sex in Cladocera as 

 controlled by Environment. 



The paper (after a very brief statement of the necessary essential descriptive 

 facts) treats the following topics as relating to Moina macrocopa : (1) Occurrence of 

 males in nature. Data showing the production of males in experimental cultures 

 (2) by crowding the mothers (accumulation of excretory products), (3) by low tempera- 

 tures, (4) by chloretone and other chemical treatments; (5) the lowered rate of develop- 

 ment of the mother as associated with these treatments; (6) means of restoring the 

 rate of development to normal and thus preventing male production by mothers 

 whose sisters, without the secondary treatment, produce males; (7) comparison of 

 times of egg-laying of eggs destined to become females and those becoming males ; 

 (8) rate of development of embryos of the two sexes; (9) the clear-cut association of 

 male production with lower rate of development and of female production with the 

 normal rate of development ; ( 10) relation of results of this study to other results on 

 sex control. 



