REPORT ON THE HOLOTHURIOIDEA. 59 



5 to 6 mm.; in their fully extended state they appear to have a greater length. 

 Those processess communicate with both of the dorsal ambulacra, three with each. 

 On examining the inside of the body-wall one discovers three pairs of ambulacral 

 cavities (PI. XLI. fig. 5) disposed one a little in front of the other ; the first pail of 

 these cavities is in connection with the two middle processes, the posterior pair with 

 both of the outermost processes, and the middle ones with each of the others. In one 

 individual I observed in front of those processes eight papillae far separated from 

 each other, and so small that they were scarcely distinguishable to the naked eye ; their 

 nature will be discussed further on. The perisoma, being particularly thick, soft, and 

 spongy, seems to be in a very macerated condition ; on its surface it is easy to 

 distinguish by the naked eye a number of small holes (PI. XXXIX. fig. 3) which 

 give the integument a porous aspect ; they enter small csecal cavities, the function 

 of which I have not been able to understand. As stated above the calcareous sub- 

 stances are quite dissolved, but the membranes which have surrounded the deposits 

 are, on the contrary, easy to discover ; by staining them in hsematoxylin, one is able to 

 form a correct idea of their former aspect (PI. XXXIX. fig. 7). From a common centre 

 three straight, sbghtly spinose arms, about 0'2 mm. long, run out, forming angles of 

 equal size with each other ; each arm gives off, close to the centre, a process directed 

 obliquely outwards. Whether some deposits of another shape occur or not, it is difficult 

 to decide, though I have thought I could detect traces of curved, spinose and unbranched 

 spicula. It is also impossible to tell either the shape of the calcareous ring, or whether 

 the madreporic canal has deposits or not. 



The polian vesicle measures about 30 or 35 mm. in length. Though I have 

 not been able to discover any pore of the madreporic canal I have succeeded in 

 following the canal itself in its passage through the thick perisoma, and am thus 

 persuaded that it really communicates with the exterior. The narrow alimentary canal 

 terminates posteriorly in a very large and wide cloaca, which towards the left side 

 has a remarkably large csecal prolongation which ascends towards the middle of the 

 peritoneal cavity ; the breadth of the prolongation is about half that of the body or 

 sometimes more. The reproductive organ is elongated and almost as long as the 

 body itself, it is constituted by a single fascicle of numerous small cseca. The common 

 efferent duct divides, where it penetrates the perisoma, into a number of larger and 

 smaller narrow canals, which pass through the integument and end in the tops of the 

 above-mentioned very small papilla-like dorsal processes. The organ is situated on the 

 left side of the peritoneal cavity. 



Achlyonice lactea, n. sp. 



Body oval, about twice as long as broad. Mouth anterior, subventral. Amis 

 posterior, dorsal. Tentacles eleven or twelve, of nearly equal size; their terminal pari 



