383 



p. HERBERT CARPENTER. 



adult, i. e. with the anal interradius backwards, and the course 

 of the gut is shown by dotted lines. Ludwig showed two years 

 ago 1 that the water-pore is in the same interradius as the fore- 

 gut, viz. the right posterior one, or south-east as it may be 

 called. When seen from the dorsal side, the gut winds in a 

 direction opposite to that of the hands of a watch, i. e. from 

 right to left, and the water-pore is in the next interradius beyond 

 the anus. The gut of the larval Asterina winds in the same 

 direction as that of the Pentacrinoid ; and when seen from the 

 dorsal side the madreporite of the Starfish, larval and adult, 

 occupies precisely the same position with respect to the anus as 

 that of the Pentacrinoid does^ (fig. iv, w.p.). Does not this go to 



W.Jl. 



Fig. IV. — Apical system of a larval Asterid {Asterina gihbosa), in -which 

 the water-pore (w./).) comes into relation with a genital plate (3) at a 

 comparatively early stage of development, slightly altered from Lud- 

 wig. ia- Interambulacral plates, im. Intermediate plates. The 

 course of the gut is indicated by arrows. 



prove that the dorsal side of the Starfish corresponds to the 

 dorsal side of the Crinoid, and not to the ventral side, as it must 

 according to Ludwig's theory? 



Both in the Crinoid and in the Ophiurid the primary water- 

 pore pierces the oral plate at a point which is not in the middle 

 line of the plate; but, as seen from the dorsal side and counting 

 in a direction opposite to tliat of the watch-hands, it is slightly 



1 ' Zeitschr. f. wiss. Zool.,' Bd. xxxiv, pp. 315-318. 



2 Ludwig, for embryological reasons, regards the anal interradius of a 

 Starfish as anterior. Abler pens than mine will doubtless discuss this 

 question. I have simply " orientirt " the Starfish in correspondence with 

 the natural position of a Crinoid. 



