46 ANIMAL PARASITES AND MESSMATES. 



We ourselves, some years ago, while making some 

 researches among the Turbellaria, found among the 

 eggs of some ordinary crabs of our coasts {Carcinus 

 mseiias), an interesting worm which we named Polia 

 involuta, but which Prof. KoUiker appears to have known 

 before, and designated by the name of Nemertes carcino- 

 philus. It is not known whether it plays the same part 

 as the Histriobdellse and the Udonellse. Delle Chiaie, as 

 well as Prof. Frey and Prof. Leuckart, make mention of 

 another nemertian which inhabits the Ascidla mamillata. 

 Among the nemertians, we may allude to the Anoplodium 

 parasita, which lives in the Holothuria tuhulosa, and the 

 Anoplodium Sclineideriiy inhabiting the intestines of the 

 Stichopus variegatiis. 



According to Mr. A. Agassiz, a species of Planarian 

 (Planaria angulata, Mull.), lives as a free messmate 

 on the lower surface of the Limulus, and prefers to 

 establish itself near the base of the tail. Mons. Max 

 Schultze recognized last year this same messmate on a 

 limulus, which had died at Cologne in the large aqua- 

 rium, and which had been sent to him for his anatomical 

 studies. He showed at the congress of German natural- 

 ists at Wiesbaden, in 1873, the drawing which he had 

 made of this animal, which he thought new to science. 

 We may remark in passing, that he arrived, by means of 

 his anatomical observations on Limuli, at the same 

 result as did my son by his embryogenic observations, 

 namely, that these supposed crustaceans are to be re- 

 garded as aquatic scorpions. Mr. Leidy also makes 

 mention of Planarian parasites {Bdellura), with a sucker 

 at the extremity of the body ; and Mons. Giard noticed 

 a blue one on the body of a Botryllus. 



