422 REPORT ON ZOOLOGY, MDCCCXLIV. 



Darwin and Krohn. Although the systematic position of 

 the animal is not, in fact, as yet determined, and Krohn, 

 from his particular researches, is inclined to place it in the 

 class Annulata, I here follow D'Orbigny's opinion, referring 

 it provisionally to the Heteropoda. It must be confessed 

 that the difference of its organization from that of the other 

 genera of this division is very considerable, yet we find 

 among the Annulata fewer points still of relationship which 

 might justify its arrangement in that class. 



Darwin's Observations on the Structure and Propagation 

 of the Genus Sagitta (Annals, xiii, p. 1) relate to Sagitta 

 hexaptera, D'Orb. Besides the well-known unciform teeth, 

 of which, in this species, eight are present on each side, 

 there occur close to the mouth two other rows of exceed- 

 ingly minute teeth. The animals affix themselves frequently 

 by the caudal fin, never by the cephalic portion [or by its 

 teeth] to other objects. Of digestive organs an intestine 

 only is present. No nucleus, no branchiae, no liver. In 

 quite young animals the author remarked a distinct pulsat- 

 ing organ in the anterior part of the body ; at a later period 

 no heart nor vessels were to be perceived. There are two 

 ovaries lying near each other in the length of the body, 

 anterior to the caudal portion, which open laterally between 

 the posterior pair of fins. In the tail itself the author 

 observed a distinct circulation of a granular matter, in two 

 columns, separated by a longitudinal septum ; he regards 

 this as an organ for the preparation of the ova of the ovary. 

 Information is given respecting the ova and their develop- 

 ment. They are pointed at one extremity and contain a 

 small nucleus. The point swells out into a globular form 

 soon after the egg quits the ovary, becomes filled with a 

 granular substance, and communicates with the granular 

 globule in the interior of the egg, so that the egg consists 

 of two nearly equal-sized globules, one of which contains the 

 granular substance, and the other is empty; then the two 

 balls separate from each other. The whole phenomenon 

 was effected in about ten minutes. 



