122 H. H. NEWMAN. 



the intestine, so as to have its blind end pointed forward on the 

 opposite side of the body. Thus these two posterior outgrowths 

 cross one another and encroach on each other's territory, a condi- 

 tion that could not well represent any ancestral state, but one to 

 be expected in a double monster such as I believe this to be. Each 

 madreporic canal connects broadly with the dorsal wall of its 

 respective hydroccel, slopes slightly toward the median line, and 

 opens by a distinct pore to the exterior. The two pores are not 

 very close together in this specimen. The other two larvae are a 

 little smaller and less advanced than that shown in Fig. i. That 

 shown in Fig. 2 is about 6 mm. in length, has no pronounced for- 

 ward growth of the preoral ccelom and does not show an over- 

 lapping of the posterior extensions of the right and left cceloms. 

 The pores of the two pore-canals are very close together and 

 might form one double madreporite. The specimen shown in 

 Fig. 3 was of about the same stage of advancement as that in 

 Fig. 2 but differs primarily in the fact that the right madreporic 

 pore is closed and its canal is smaller and shorter than its left 

 partner. Also the anterior cceloms have not fused. 



In discussing these anomalous larvae with Dr. Walter K. Fisher, 

 director of the Hopkins Marine Station, I was interested to learn 

 from him that he had, while collecting, noted adult specimens of 

 Asterina, and of other species of asteroids, in which there were 

 two madreporic plates and, correspondingly, two stone canals. 

 This information immediately suggested to me the strong prob- 

 ability that these adults with paired madreporic plates must 

 have arisen from larvae with double madreporic pores such as I 

 had under observation. The question would then arise as to 

 whether this double condition in the adults would bear the same 

 phylogenetic interpretation as has been offered for the double 

 condition in the larvae. If not; why not? But this involves us 

 in a discussion of the significance of these anomalous paired struc- 

 tures in echinoderms. 



DISCUSSION. 



Three distinct interpretations have been offered for the appear- 

 ance of these anomalous right-hand elements that normally 

 appear only on the left. 



