44 SUMMAKY OF CUREENT RESEAECHES EELATING TO 



Anuulata. 



Behaviour of the Earthworm.* — H. S. Jennings inquires into the 

 factors which determine the direction in which the earthworm moves. 

 When a local stimulus is applied to one side of the anterior part of the 

 earthworm, any one of the following varied methods of action may 

 result : there may be merely a slight swelling of the region stimulated ; 

 the worm may turn the anterior end away from the side stimulated ; it 

 may turn the head towards the side stimulated ; it may creep backward, 

 or forward, or first backward and then forward ; the head may be 

 merely retracted ; the animal may make a sudden right-about-face, in- 

 terchanging the position of anterior and posterior ends ; the anterior 

 fourth of the body may be raised in the air and waved wildly about. At 

 least nine different methods of behaviour may follow the stimulus. 

 What are the determining factors ? 



The following groups may be distinguished : — A. External factors : 

 (1) intensity of the stimulation, (2) localisation of the stimulus. B. In- 

 ternal factors : (o) the reaction depends partly on what the animal has 

 done, and on its position, just before receiving the stimulus ; (4) the 

 reaction depends partly on the general tendency of the animal to move 

 in a certain way, namely, forward rather than backward ; (5) the re- 

 action depends partly on the direction in which the animal is crawling 

 at the moment when it is stimulated ; (6) the reaction depends partly 

 on previous stimuli received, according as the earthworm is in a state of 

 rest, or of moderate activity, or of excitement, of which there are many 

 different degrees. 



" The movement at a given time demonstrably depends, not alone 

 on present external conditions, but also on former external conditions, 

 former actions of the organisms, and present internal physiological con- 

 ditions that are determined in many different ways. The direction of 

 movement of one of these organisms cannot be represented as a simple 

 function of the direction of impact of some external force, but is the 

 complex resultant of many different factors." 



As in his experiments on Infusorians, so here Jennings finds evidence 

 that stimulation causes varied movements, which do not all lead toward 

 the condition finally attained, and that those movements which do lead 

 towards this final condition (the " optimum ") are followed up more 

 decidedly than the others. The behaviour may perhaps be most accu- 

 rately characterised as " selection from among the conditions produced 

 by varied movements." 



Maturation and Fertilisation in Saccocirrus.f — F. Hempelmaun 

 describes the processes of oogenesis, maturation, and fertilisation in 

 Saccocirrus jMpiUocercus, and finds that they follow the regular routine. 

 One remarkable fact, however, is that the spermatozoa pass by a direct 

 route of communication between the receptaculum and the ovary, that 

 they make their way into the latter, and penetrate even half -ripe oocytes. 



* Journ. Exper. ZooL, iii. (1906) pp. 435-55 (1 fig.), 

 t Zool. Anzeig., xxx. (1906) pp. 775-84 (19 figs.). 



