408 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of the way in Tvhicli star-fishes and brittle-stars right themselves, or return 

 to their normal position ; the description given by Mr. Eomanes and 

 Prof. Ewart is, generally, exact, but the exact method of righting is not the 

 same in all the species of star-fishes, though brittle-stars much more closely 

 resemble one another. The experiments were varied by the application 

 of drugs, differences of temperature, and weights. The result of all is the 

 definite conviction that the movement is not due to any external peripheral 

 reflex stimulation. The impulse which comes to the central organ, or (in 

 Asterids) to tlie subordinate centres of the radial medulla of separate 

 pieces of the rays must, it may be thought, be either central or centripetal ; 

 against the former supposition, which would be explained by imagining 

 that the abnormal position had caused a disturbance of the circulation, 

 Prof. Preyer cites certain experiments on frogs ; and the same objection 

 may be raised to the second suggestion. What explains the righting of 

 frogs — namely the " muscular or innervation sense " — may be applied also 

 to Echinoderms. 



The memoir concludes with some observations on movements away 

 from an object, such as an attemjit by an Ophiurid to get away from or free 

 itself of a tube drawn over one of its arms; the author describes the five 

 different ways in which the brittle-star acted ; when the tube was loose, it 

 tried to rub it off by drawing along the floor of the aquarium ; when the 

 tube was rather tighter it tried to shake it off", or held it down with the 

 neighbouring arms and tried to draw the median arm out, or it tried to 

 push it oft* with the two neighbouring arms, or it broke off the arm that 

 was covered by the tube. It is impossible to refer such phenomena as 

 these to simjde reflex action ; the Ophiurids rather possess the power to 

 adapt themselves to quite new situations, such as they have not experienced 

 before. If intelligence dejoends on the power of making experiments, that 

 is of learning, and making use of what is learnt in a new way, then 

 Ophiurids must be very intelligent. Complicated movements of a like kind 

 were never seen in Asterids. 



Homologies of Larvae of Comatulidse.* — M. J. Barrois thinks that the 

 facts that the closure of the blastopore of the larva is effected not far from 

 the spot at which the opening of the calyx appears later on, and that the 

 ventral pit corresponds in situation to the buccal invagination of the 

 other larvaB of Echinoderms, should show us that we ought not to consider 

 the region of the calyx as anterior and that of the peduncle as posterior, 

 but vice versa ; the i^entacrinoid, then, cannot be considered as arising from 

 a larva fixed by its posterior part, but as one fixed by its preoral lobe. 



Eesearches on the metamorphoses of Echini have led the author to 

 conclude that the larva ought to be considered as being composed of two 

 parts, an anterior formed by the portion which projects above the subum- 

 brella, that is, the preoral lobe and the oesophageal region, and of a posterior 

 part composed of the rest of the body ; during metamorphosis the former 

 is detached at its base, and the latter is transformed into the urchin. These 

 two parts correspond to the two fundamental divisions (calyx and peduncle) 

 of the larvae of Comatulids. 



Ccelenterata. 



Natural History of Hydra. t — Continuing his studies on the divisibility 

 of living matter Herr M. Nussbaum has devoted his attention to the genus 

 Hydra, of which he gives a monographic account. 



* Coroptes Rendus, ciii. (1887) pp. 892-3. 



t Arch. f. Mikr. Anat., xxix. (1S87) pp. 265-3GG (8 pis.). 



