M. Leuckart on the genus Sacculina. 425 



sequently been confirmed by tbe investigations of Oscar Schmidt*. 

 Schmidt likewise observed the larvae of Peltogaster (Sacculina) 

 Carcini, and by that means, independently (without knowing 

 any other investigations than those of Rathke), arrived at a cer- 

 tain conviction that here we have to do with a Crustacean of the 

 group Parasita, 



The similarity of these animals with the Lerncpadce could not 

 escape Steenstrup ; but, unacquainted as he was with the inves- 

 tigations of Thompson and Schmidt, by putting together Pelto- 

 gaster and a parasite with Onisciform young also observed in 

 Crabs by Cavolini, and by the apparently accordant statements 

 of llathke that a small Onisciform Crustacean, described as 

 Liriope pygmaa, Kathke, sometimes occurred in the brood-cavity 

 [Bruthbhle-j stomach of Rathke), he allowed himself to be 

 misled into arranging our parasites with the Isopod genus Bo- 

 pyrus. 



It is, however, scarcely to be doubted that Steenstrup has 

 now given up this opinion, especially since Kroyerf and Lind- 

 strom { have published their observations on the larval state of 

 the species of Peltogaster, which are exactly conformable with 

 the other statements. It appears, however, from the investiga- 

 tions of the former, as though the young state of the different 

 species presented many diversities ; at least, he states that the 

 larva of one species of Peltogaster, and of the small and globular 

 form parasitic upon Hippolyte [Sylon, nov. gen.) belonged to a 

 more advanced period of development than those of a second 

 species of the genus Peltogaster, which latter (as may also be 

 asserted of those of the genus Sacculina, according to Schmidt) 

 agree closely with Cavolini^s figures, that is to say, present a so- 

 called Nauplius-iovm. The anatomical investigations furnished 

 no decisive result, and left the author himself in doubt as to the 

 existence of a mouth. 



I have had but few opportunities of observing these remark- 

 able animals, — first at Heligoland in the year 1846, afterwards 

 at Nice, and again a few weeks ago, in company with Dr. Pagen- 

 stecher of Heidelberg, at Heligoland. The first time I met with 

 Peltogaster Paguri, Rathke, at the latter place, and the second 

 time with a Sacculina, but of each only a single example. The 

 Sacculina was attached, as usual, to the tail of a Crab, Hyas 



* Zeitschr. fiir die ges. Naturwissenschaften, Halle 1853, p. 101 ; Hand- 

 atlas der vergl. Anat. taf. x. fig. 7 ; a third memoir in the Journal the 

 * Weltall,' 1854, p. 19, is still unknown to me. 



t Ofvers. Kongl. Dansk. Vid. Selskab. Forhandl. 1855, p. 12/, trans- 

 lated in Zeitschr. fiir die ges. Naturwiss. viii. p. 41.9. This paper of 

 Kroyer's is, however, only to be regarded as a preliminary one. I do not 

 know whether a more com})lete memoir by our author has since appeared. 



:|: Ofvers. Kongl. Vetensk. Akad. Forhandl. 1856, xii. p. 361. 



