( «73 ) 



aboui 0.15 AI. They will nol exceed however those <>n the Sue2- 

 canal with a strong wind. 



For ilic lasl 16 l\. Al. of such an open canal the maximum 

 velocities al springtide may l>c somewhal more considerable. <m 

 accounl however of the ureal width, which mav be given to this 



par! they will cause no serious difficulty. 



Therefore, if we assume, as we have good reason to do, that even 

 at spring tide and with wind the velocities of the curreni on the 

 Suez-canal oiler no serious difficulty to navigation we maj conclude 

 thai on a Panama-canal of the above description also navigation will 

 experience no difficulties on accounl of the velocities of the current. 



Therefore, if we leave out of consideration the question whether 

 an open Panama-canal withoul tidal lock is to be preferred either 

 to a sea-level canal with Buch a lock, as proposed by the Board of 

 Consulting Engineers, or to a summil level canal with three locks, 

 as is now in course of execution, we may conclude, in the main 

 in conformity with the conclusion of the French Academy of Sciences 

 of 1887, but for different reasons: 



That the velocities of the current due to tidal motion in an open 

 Panama-canal without tidal lock will be no obstruction to navigation. 



Zoology. - - "On the formation of red blood-corpuscles in the placenta 

 of the flying main (Gakopithecus). By Prof. A. A. W. II brrcht. 

 (Communicated in the meeting of March 30,1907). 



At Hie meeting of November 26, 1898, I made a communication 

 on the formation of blood in the placenta of Tarsius and other 

 mammals, which was later completed by a more extensive paper, 

 containing many illustrations (Ueber die Entwicklung der Placenta 

 von Tarsius nnd Tupaja, nebsl Bemerkungen liber deren Bedeutung 

 als hnmatopoieiische Organe; Report 4 th Intern. Congress of Zoology, 

 Cambridge 1898). The Tacts observed by me and the interpretation 

 founded on them, have not until now been generalij accepted, and 

 in a recent very extensive discussion of the position of the problem 

 concerning the origin of the ra(\ blood-corpuscles in the 14"' volume 

 of the "Ergebnisse der Anatomie und Entwicklungsgeschichte" ^Wies- 

 baden 1905), by F. Wbidbnrbich, the author, when mentioning mv 

 views, emits the supposition thai I mixed up phagocytic and haemato- 

 poietic processes. 



This conclusion was not based on a renewed and critical exami- 

 nation of the material, studied by me. I have regretted this, since 

 I have pointed out clearly and repeatedly that the numerous prepara- 



