4 E. W. MACBPJDE. 



second point, the occurrence of " Gitterplatten " (lattice-plates) as ralcarcous bodies is of 

 common occurrence in the genus Cucumaria. Now, in the number of tentacles, the 

 presence of an introvert, and the shape of the calcareous bodies our specimens resenil >le 

 Cucumaria. In the presence of tube-feet on only three, radii, they resemble Psolus 

 [and Colochirus, F.J.B.], but in Psolus the body is flattened on one side so as to 

 form a creeping sole, whereas in our specimens the body is almost cylindrical, as in 

 Cucumaria. But to me the strongest evidence of their relationship to this genus 

 is seen in their resemblance to the young Cucumaria probably C. lactea, which I 

 obtained at Plymouth in 1905, one of which is shown in fig. 4. Here too we find 

 that the tube-feet are not developed on all the interradii, but are confined to two. 

 Prof. Ludwig (4) notes that in the development of C. planci a pair of tube-feet 

 are formed at the termination of the median ventral water-vascular canal and remain 

 for a considerable time the only tube-feet. These two terminal tube-feet are clearly 

 marked in transverse sections of our specimens (PI. II., fig. 8c). 



Our specimens, then, belong to the genus Cucumaria, but they show as yet no 

 obvious traces of the characteristic pulmonary trees. They are, however, quite adult 

 in their mode of obtaining food, for the stomach is filled with the half-digested remains 

 of Algge. 



It would seem that a similar stage occurs in the development of Stichopus 

 japonicus. Professor Mitsukuri (8) has found that the just metamorphosed form has 

 " a coat of armour," consisting of " disked tables with tall spires united by several 

 cross-beams, which cover the body thickly, their liases even overlapping one another 

 when slightly contracted. The ventral pedicels were in three rows." 



PI. I., fig. 5 shows a longitudinal sagittal section through a specimen in which the 

 course of the alimentary canal is quite straight, and in which both mouth and anus are 

 involved. No endeavour has been made to represent the histology, but the general 

 relationships of the organs are clearly shown. The mouth leads into an oesophagus 

 surrounded by a very thick layer of muscles. Un this follows a long conical stomach 

 filled as noted above with Algae. The stomach leads through a short intestine into 

 the thin-walled cloaca which is attached to the sides of the body-wall by muscular 

 strands traversing the ccelom. I was at first inclined to think that our specimens 

 might be older stages in the development of Cucumaria crocea, the embryos of which 

 have been described by Mr. Simpson and myself (6). But this cannot be the case, for 

 in these embryos the alimentary canal is already folded. The stone-canal ends blindly 

 in a thin-walled sac (ax., fig. 5) embedded in the body-wall ; there is no pore-canal 

 leading from this sac towards the exterior such as was described by Mr. Simpson 

 and myself in the case of the embryos of Cucumaria crocea in an earlier report, 

 nor is there as yet any communication with the body-cavity such as exists in the 

 adult Holothurians. This sac corresponds to the axial sinus of other Echiuoderms. 

 The genital base (PI. L, <j. l>., fig. 5), from which spring the rudimentary 

 genital organs, may be seen close to the stone-canal, but there is as yet no genital 



