24 



La Valette St. George. The germ cells are very large and the number 

 of chromosomes can be determined with certainty. Normally there 

 are twenty-eight chromosomes although in rare cases we find them 

 to be twenty-six or twenty-seven. They arrange themselves not in two 

 rows as Henking and vom Rath state, but in a single row and 

 their division takes place transversely to their longitudinal axis as 

 Ischikawa first observed in Diaptomus. After this division, the 

 daughter cells prepare to divide with no resting stage. In this second 

 division, »each chromosome does not become divided into two as usual, 

 but remains undivided during the division« (Ischikawa), so that 

 fourteen of the twenty-eight go bodily into one cell and the other four- 

 teen into the other. Consequently, the daughter cells of the second 

 division contains only fourteen chromosomes > which is half the num- 

 ber of the original. 



IV. The zone of Metamorphosis. After this second division, the 

 chromosomes arrange themselves like a moniliform ring round the 

 periphery of the nucleus and form the head of a spermatozoon. 



A large »Nebenkern« also appears and forms together with the 

 cell protoplasm the tail of a spermatozoon. This »Nebenkern« consists 

 of the remains of »Verbindungsfäden (c after division , and is different 

 from the »Nebenkern« of the germ cells in the growing zone. 



A mitosome is clearly to be seen in preparations stained with 

 Böhmer' s Haematoxylin. This is formed from the coalescence of a 

 few small granular spots appearing in the cytoplasm, showing its origin 

 from the cytomicrosomes. Meanwhile , the chromosomes coalesce into 

 a single mass and the »Nebenkern« elongates and a spermatozoon with 

 a spindle shaped head and an elongated tail is formed, while the mito- 

 some gradually becomes fainter and fainter till at last it disappears. 



A full account of this investigation with plates will , I trust, be 

 shortly published in the Bulletin of our College. 



Tokio, 26th October 1893. 



3. On a new Balanoglossus Larva from the coast of California, and its 

 Possession of an Endostyle. 



By Wm. E. Ritter, Ph.D., Assistant Professor of Biology, University of 



California. 



eingeg. 12. December 1893. 



During the summer of 1893, the marine biological laboratory of 

 the University of California was located at Avalon , on the island of 

 Santa Catalina, about twenty -five miles off the coast of Southern 

 California. 



