M. Leuckart on the gentts Sacculina. 425 



scqucntly been confirmed by the 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 Lemccache 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 Rathke that a small Onisciform Crustacean, described as 

 Liriope pygnuca, Rathke, sometimes occurred in the brood-cavity 

 (Bruthuhle ; 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 X 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 Xauplius-fovm. 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 w r itk 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. fur die ges. Xaturwissenschaften, Halle 1853, p. 101 ; Hand- 

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

 ' Welt all,' 1854, p. 19, is still unknown to me. 



f Ofvers. Kongl. Dansk. A'id. Selskab. FSrhanill. 1855, p. 12/, trans- 

 lated in Zeitschr. fill' die ges. Naturwiss. viii. p. 419. This paper of 

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

 know whether a more complete memoir by our author has since appeared. 



X Ofvers. Kongl. Yetensk. Akad. Forhandl. 1856, xii. p. 361. 



