Nos. 451-452.] AMERICAN SOCIETY OF ZOOLOGISTS. 51 I 



described as roughly triangular. The two b 

 triangle (Fig. 5) are really the rudiments of tl 

 of the larva, which throughout the whole lar 

 much longer than the rest, and are the most 

 of locomotion. The cells which form the int* 

 close of segmentation are now seen to be dest 

 supporting calcareous rods for these arms, ar 

 attribute the leading peculiarity of the devek 

 appearance of a solid morula instead of a hollo 

 extremely precocious formation of the skeleti 



On the Homologies of the Archcnteron and Bhv 

 brates: Charles S. Minot, Harvard Universit)-. 



Medusa Fauna of the Bahamas : Alfred < 

 Brooklyn Institute of Arts and Sciences.— The 



of the Bahamas is poor m compans* 



. with that of the Tortu 



The writer secured ninety (90) species of Hydr< 

 medusae, ScyphomedusaD, Siphonophorae and Ctenophorse at th 

 Tortugas, while only forty-three {43) species were found at tli 

 Bahamas. What is more interesting, the relati\e abundance . 

 specific forms is quite different in the two regions. 1 be c<.n 

 monest medusa during the summer month, at tlie Trntuga 

 Pseudoelvtia pentata, is m.t found at the P>ah.nna.. and ll 

 commonest medusa during the summer mr)nths at ibc Hahania 

 Lymnorea alexandn, is not found at the Tortn.ua.. 



Altogether, of the forty-three species ot Habama ine.hi.. 

 twenty-three (23) are about eciuall) abundant (m tbeotbrrsu 

 of the Gulf Stream at the Tortugas. Sixteen are nmiv a,Mi 

 dant at the Bahamas than at the lori;.-,.i-, vvbi c l- .1 a.^ ni" 



abundant at the Tortugas. This 1- 



ing facts : The Tortugas lie to b-v ' ^"i ■ 



the extraordinarily rich pelagic liu' ^ ' ' ' 



stantly driven upon their shores, wbne w-y r-.....^:ii ■■- be t<. l 

 windward of the stream and their local tauna 1.. nut "^^^"^^^ 

 by creatures characteristic of the great curient. leic 

 however, something more than a mere concentration ot mc i\i 



