ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 233 



sets in, cells budded in from the centre of the hydroccele fill the mesen- 

 teron. The right and left body-cavities, now dorsal, grow round original 

 ventral side, and each forms a longitudinal mesentery near the original 

 ventral radius. The mouth appears as a depression in the wall of the 

 vestibule. Into the now small anterior body-cavity opens the stone- 

 canal, running from the water-vascular ring in the oral longitudinal 

 mesentery, and not in direct continuity with the water-pore. The anus 

 opens in the same interradius as the water-pore. 



(4) Skeleton. Shortly after the disappearance of orals and basals, 

 three plates are developed at the posterior end of the stem, the homo- 

 logues of the under-basals of the dicyclic Crinoids. After fixing they 

 fuse with one another and with the top-stem-joint, so as to form a largo 

 plate, hitherto mistaken for a simple centrodorsal. 



New Features in Pelanechinus corallinus.* — The most interesting 

 point, perhaps, in Mr, T. T. Groom's account of Pelanechinus corallinus is 

 the discovery of pedicellarire in a fossil species ; the author has found 

 them " in great variety and abundance, and in beautiful preservation." 

 The only good mode of examining them is to put the whole urchin on 

 the stage of the compound Microscope and to illuminate it well ; if this 

 method were adopted, Mr. Groom believes that pedicellariae would be often 

 found on fossils. In Pelanechinus all these organs are trivalved, and of 

 these three distinct varieties were found, which are described and figured. 



Budding in Star-fishes.t — Herren P. and F. Sarasin give a figure of 

 a specimen of Linckia multijpora, in which the process of regeneration 

 has resulted in the formation of a quite new star ; in this case we have 

 to do with two stars connected with one another, and so giving the 

 appearance of a true animal colony. But they allow that these colonial 

 formations are to be regarded as abnormalities. However, there is no 

 sharp limit between pathology and variability, and so facts of this kind 

 are always of significance. Fuller details are promised. 



Mediterranean Synaptidse.| — Di\ R. Semon continues his account 

 of the Synaptidse of the Mediterranean. The calcareous ring commences 

 to be formed at a time when the rudiment of the water-vessel in the 

 Auricularia-l&wa, consists of a horseshoe-shaped tube with the out- 

 growths which will form caBca, primary tentacles, and radial vessels ; 

 they arise as simple rods on the convex side of the tube, and, in corre- 

 spondence with the number of tentacles, there are at first only five ; we 

 see then the relations which they have to the tentacles. This is further 

 shown by the fact that the joints of the calcareous ring increase in 

 number simultaneously with the tentacles. These facts bear on the 

 question of the homology of the calcareous ring with some of the hard 

 parts of the Echinoidea. Dr. Semon thinks that before we proceed to 

 speculate on this point we must get some proof of a skeletal part of an 

 Echinid holding the same relation to the five primary tentacles as do 

 the parts in question in a Holothurian. The ring not only serves as 

 origin for the tentacles — which appears to be its primary function — but 

 also for the insertion of the semilunar valves described by Hamann. 

 When the longitudinal musculature of the tentacle is relaxed that organ 

 lies extended in a straight line, and the valve (in consequence of the 



* Quart. Journ. Geol. Soc. Lond., xliii. (18S7) pp. 703-14 (1 pi.). 



t Zool. Anzeig., x. (1SS7) pp. 674-5. 



X MT. Zool. Stat. Neapel, vii. (1887) pp. 401-22 (1 pi.). 



