264 



a spermatozoon. In the case of the Aphides, the females which 

 are produced directly from the act of impregnation, retain in 

 themselves the property of awakening the power of development 

 in the ova produced in their ovaries, and this power is trans- 

 mitted from one brood to another until it finally dies out, — a 

 process which seems to have its analogue in the disposition to 

 the production of adventitious growths in the ovary, which is 

 sometimes seen to be hereditary in the human female. In the 

 Humble Bee it would seem that the ova from which the first 

 brood are produced, are fertilized directly by spermatozoa; 

 that ova transmit the awakened force to those which produce the 

 second, and these in their turn to those which produce the third. 



Mr. Girard read descriptions of two marine species of 

 Planariae, in addition to those given at the last meeting, as 

 follows : — 



VoKTEX Warrenii Girard. General form elongated, sides 

 nearly parallel ; anterior and posterior extremities rounded. 

 Small species, reddish brown, found on the shores of Boston Har- 

 bor. Not common. 



Vortex Candida Girard. Body elongated, tapering away 

 towards the posterior extremity ; head rounded ; sides entire ; 

 almost transparent, of a pale rose color. From Chelsea beach, 

 found attached to the Horse-shoe Crab. Length, a quarter of an 

 inch. 



The generic position of these two species is still a matter of 

 doubt ; the genus Vortex not being as yet well circumscribed. 



He then gave a brief account of the fresh water species 

 of this family, known to him as the inhabitants of this 

 country, as follows : — 



Planaria gracilis Haldem. Suppl. to a Monogr. of Limn. &c. 

 1840, p. 3. Common about Cambridge in pools and rivulets. 



Planaria tigrina Girard. Of this species I have seen but 

 one individual in a damaged state, but showing itself distinct 

 from all those I have known, being of a dark brownish color, 

 dotted with large white spots, and smaller and more numerous 

 black ones. Found in the State of New Jersey. 



