70 MtsceUancous. 



nnd nlidorainal RCjrincnts of tUe jiorniiniil streak. The seofmont 

 ■which l)oars tho clielioene is scparatid lator than the remainder t>f 

 the thoracie sejrments. at a period -wlien from three to four abdo- 

 minal segments have arisen from tlie caudal section; 



11. Tho segmentation of the appendages appears at a somewhat 

 early stage ; 



lii. There are no emhryonic envelopes; 



13. A flexure of the embryo takes place, as in the Ara- 

 neina ; 



14. The lateral organs, which were described by Croneberg *, 

 are represented in younger stages by large elongate vesicular sacs, 

 which are connected with the body above the first pair of legs by 

 means of a thin stalk. In the young immediately after V)irth the 

 lateral organs are considerably diminished in size and shrunken. 

 In the adult animal, apparently, the linguiform triangular folds of 

 skin which are found beneath the mandibles must be regarded as a 

 remnant of the lateral organs. — Bioh(/is'ches Centralblatt, xii. lid., 

 no. 2-2 (November 15, 18U2), pp. 687-089. 



On Tuo Species of !Myzostoma pcimsiiic upon Antedon phalangium, 

 MuUer. By M. Kexri PRorno. 



Antedon phalanfiium is tho host of two species of Myzostoma 

 described by von Graff under the names Mi/zostoma pidvlnar and 

 J/, (ilattnn, and which were both discovered in the Minch during 

 the expedition of the ' Porcupine.' I have met with these two 

 parasites on their usual host in the dredgings made in the course 

 of last summer by the boat belonging to the Arago Laboratory ; 

 and this enables me to communicate forthwith certain interesting 

 features in the history of these Myzostomidtc, which are so little 

 known. I pass over the anatomical and histological details, which 

 will be dealt with elsewliere. 



Mifzostoma puh'inar.—Keir von Graff, whose description of this 

 species was founded upon a unique sjjccimen, has well characterized 

 its external form ; he has drawn attention to the dorsal jjosition of 

 the mouth and the cloacal orifice, but he must have been led astray 

 bv the bad state of preservation of the specimen which he studied, 

 for he states that the organs which are known in the other species of 

 Mifzostoma under tho name of suckers are absent in this form, 

 though these structures are really present, although not so well 

 developed as in the majority of the other species. 



Contrary to the opinion of von Graff, Mijzostoma ])rih'inar does 

 not live upon the disk of Antedon plialangium ; it inhabits the 



♦ A. Croneberg, " Ueber ein Entwicklungsstadium von Galeodes," 

 Znol. Anz., 10 Jiihrp., 1887. 



