67 



movements a minute i.e. the same number as found in full-grown 

 animals. 



III. As yet no support has been found for the opinion that small 

 but full-grown individuals of a certain s[)ecies have more rapid 

 intestinal motion than bigger individuals of the same species. 



The following experiment s h o w s t h a t i t is n o t 

 the size or the age, but the kind of individual 

 w li i c h affects t h e i n t e s t i n a 1 m o v e m e n t s. 



The intestine of a half-grown rat of 86 grammes (i.e. as heavy 

 as the above-mentioned rabbit of 3 days) as well as the intestine of 

 a guinea-pig 9 times this weight, (777 grammes) contracted exactly 

 twice as rapidly as the intestine of the rabbit (rat and guinea-pig 35, 

 rabbit 16—18 a minute). 



A number of questions are connected with these facts. First the 

 movements of the various parts of stomach and intestinal channel 

 must be compared. Further birds and cold-blooded animals must be 

 examined. These experiments we have partly carried out already. 

 It is not sufticient to study the velocity of the intestinal movements, 

 but it should also be investigated how much labour is performed 

 by the intestine. 



In short not only the anatomy, but also the mechanical function 

 of the intestine and the various parts of the stomach and intestinal 

 channel must still more be submitted to a comparative examination 

 in the ditFerent species of animals. 



Physiological Laboratory of the 



University of Groningen February 1913. 



Paleontology. — ''The orientation of the shells of Beyrichia tuber- 

 culata Klöden sp." By Dr. J. H. Bonnema. (Communicated 

 by Prof. Moll.) 



Among the smaller fossil Ostracoda the best-known is certainly 

 Beyrichia tuberculata Klöden sp., illustrations of which are found 

 in nearly all the text-books on paleontology (1, p. 527) and strati- 

 graphical geology (2, p. 130). 



From the figures found in these books it appears that these valves 

 present a lateral aspect which is more or less oval. One of the long 

 edges is straight; the other is curved, which is also the case with 

 the two short edges. On the side there are two nodes near one 



5* 



