70 Miscellaneous, 



and abdominal segments of the germinal streak. The segment 

 whicli bears the chelicerne is separated later than the remainder of 

 tlie thoracic segments, at a period when from three to four abdo- 

 minal segments have arisen from the caudal section ; 



11. The segmentation of the appendages appears at a somewhat 

 early stage ; 



12. There are no embryonic 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 birth the 

 lateral organs are considerably diminished in size and shrunken. 

 Ill 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. — Biologisehes CentraJblatt, xii. Bd., 

 no. 22 (November 15, 1892), pp. 687-689. 



On Ttvo Species of Myzostoma parasitic nj^on Antedon phalangium, 

 ' Miiiler. By M. Henei Pkoiiho. 



Antedon jilialangium is the host of two species of Myzostoma 

 described by von Graff under the names Myzostoma pulvinar and 

 M. alatiim, 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 tbe 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 Myzostomidte, which are so little 

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

 will be dealt with elsewhere. 



Myzostoma pulvinar. — Herr von Graff, whose description of this 

 species was founded u])on a unique specimen, has well characterized 

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

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

 by 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 

 Myzostoma under the name of sucJcers 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, Myzostoma pulvinar does 

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



* A. Croneberg, " Ueber ein Entwicklungsstadium von Galeodes,'^ 

 Zool Anz., 10 Jahrg., 1887. 



