M. E. Hesse on the Pranizae and Ancei. 415 



after their capture. In a note the author says, "When the 

 Praniza are taken too young, it would appear that the nourish- 

 ment which they find in the vessels containing them is insuf- 

 ficient, as they always perish. Those hatched in my possession 

 never succeeded in passing their third change of skin. But 

 when they are at their last period, it is probable that the Infu- 

 soria and other microscopic animals which live among marine 

 plants, and the decomposed Solenue, which are reduced almost 

 to a fluid state, are sufficient for them. This is also the case 

 with the Ancei, which content themselves with this food, without 

 appearing to sufier from it. Nevertheless I have noticed that, 

 when other nourishment was wanting, the male Ancei devoured 

 their females, especially those which were weakened by the 



production of their young I have also ascertained that a 



male Anceus Manticorus ate a small dead Annelide which I had 

 given to it ; so that it appears certain that these Crustacea feed 

 both upon animal and vegetable substances, but especially the 

 former when they arc able to procure them." 



Hence it would appear that animal food is necessary for the 

 transformation of the Praniza, and that it is for this reason that 

 they attach themselves to fishes for a portion of their life. They 

 prefer those which are very viscous, such as the flat fish, gur- 

 nards, and wrasses ; and we may suppose that they absorb this 

 mucilage : but it is easy to recognize the presence of blood in 

 their stomachs, and sometimes they are so gorged with blood 

 as to be as much deformed by it as if they were filled with 



eggs- . , , , 



Upon the suctorial powers of the Praniza the author has 



made the following observations. On agitating the water of a 

 vessel containing Praniza, they attached themselves firmly to a 

 fragment of Zostera, but without employing their thoracic feet. 

 On examining them with a lens, M. Hesse saw, through the 

 tissues of the plant, that they were attached by the suctorial 

 action of the mouth, which formed a sort of disk. The same 

 thing occurs when they attach themselves to a fish : clinging 

 firmly to the fish by the two thoracic feet situated at the sides 

 of the head, and also by the hooked extremity of the rostrum, 

 they open the door-like footjaws which close the mouth beneath, 

 and apply the head to the part upon which they desire to adhere ; 

 then, by means of the orifices already described, they exert a 

 powerful suction, puncture the skin with their innermost mas- 

 ticatory organs, and pump up the fluids necessary for their 

 nourishment. 



When transformed into Ancei, these Crustacea are never met 

 with on fishes ; but most of those obtained by the author from 

 Praniza had this origin. Two species, however, are supposed 



