C \l.\\l<»( i;in i S I > l< IMED I 87 



phantom. Bui i ! i<- \ go further than Neumayer, who, with manj others 

 l.mks upon the Cystideans as the progenitors of Echinoderms, and so they 

 look upon the llolotliinians as the type from which the Cystideans, as well 

 as the other orders of Echinoderms, have been developed. The similarity 

 of some of the Psolidae to stages of the armless Cystideans goes as far to 

 prove the close relationship between the Holothurians and the Cystideans as 

 the analogy between Echinoderm larvae and Toruaria, the larva of Balano- 

 glossus, which was bo long mistaken by writers on Echinoderms for a Starfish 

 larva, furnishes the ground for establishing a close relationship between 

 the Worms and Echinoderms. The absence of a water system in Balano- 

 glossus shows this similarity to be the most superficial analogy, and to be 

 limited, as in echinodermal larvae, to a distant resemblance in the arrange- 

 ment of the vibratile cords, — a resemblance which had before misled older 

 writers to look upon the Worms and Echinoderms as closely allied types. 



Starting from the assumption, as he says, " Dass ihr [der Echino- 

 dermen] Skelet menials wirklich eine einheitliche -Masse bildet," Semon 

 loses sight of the very structural feature which is perhaps the most re- 

 markable character of Echinoderms; namely, the manifest want of con- 

 nection, I might almost say in every detail, of the internal organs with the 

 exterior plates composing the test of the various orders of the class, and 

 -which was pointed out by Midler as early as 1854. Midler* has in- 

 sisted upon the want of connection between the madreporic body and 

 the apical plates. He has admirably expressed the want of connection 

 existing between the internal organs and the calcareous plates, when he 

 says: "Zur Zeit, wo der junge Seeigel selbstandig wird und wo dieser 

 Porus an ihn iibergegangen ist, giebt es aber an dem Perisom des Seeigels 

 noch gar keine Flatten, weder Ambulacralplatten noch Interambulacral- 

 platten noch Genitalplatten. Das Verhaltniss zu den Platten ist daher 

 iiberall secundar, . . . dagegen ist die Stelle des Porus in den Larven 

 sowohl der Seeigel als Asterien und Holothurien iiberall dieselbe, auf dem 

 Riicken der Larve seitwarts der Mittellinie." 



I cannot understand the positive statement of Ludwig, " Dass bis jetzt 

 auch nicht ein einziger Fall bekannt geworden ware, in dem die Madre- 

 porenoffnungen sich von den Genitalien entfemt hatten." In Echini the 

 genitals may be entirely disconnected from the madreporic body in the 

 Clypeastroids. We should from this alone question the homologies sug- 



* Ueber den Bau der Echinodermen. Abhandl. d. K. Akad. d. Wiss. Berlin, 1S54. 



