758 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The author has recently shown that the fresh-water Eotatoria fall into 

 the two natural divisions of Ductifera and Aductifera, and into these fall 

 also a number of marine forms. For the parasites of Nehalia, a third family, 

 which may be called that of the SeisonidsB, must be instituted. It stands 

 nearer the Philodinaidse than the Ductifera. As the former appear to pre- 

 sent the most primitive arrangement of the wheel-organ, it may be supposed 

 that the Seisonidse branched off early from the root of the trunk of the 

 Eotatoria. The most primitive arrangement of the sexes was a double one, 

 and the bisexual character of most members of the class must be regarded 

 as having been secondarily acquired. The only difficulty is presented by 

 the masticatory organs, which in the Seisonidse are closely of the type which 

 obtains in the Ductifera, and different from what are seen in the Philo- 

 dinaidsB. The author is inclined to explain this by supposing that the 

 masticating apparatus of the Archirotator as seen in the PhilodinaidaD was 

 lost, and that a fresh and independent development obtained in the two 

 different divisions. 



Myzostoma Bucchicliii.* — Dr. F. v. Wagner describes, from a single 

 specimen dredged off Lesina, a new species of Myzostoma, which he calls 

 M. BuccMcJiii. As Antedon rosacea was also dredged in the neighbourhood, 

 the author thinks it may be one of the parasites of that Crinoid. The disc 

 is about 3 mm, in diameter, and the new species is characterized by the 

 tubercles which are arranged symmetrically in five groups on the dorsal 

 surface. Each consists of an aggregation of four to seven papillae of various 

 sizes. The suckers are completely wanting, as in M. folium, carinatum, and 

 coronatum. 



Echinodermata. 



Movements of Star-fishes.l — Prof. W. Preyer commences the second half 

 of his Memoir on various Echinoderms by a discussion of the reflex move- 

 ments of Crinoids. To what is known as to the function of the cirri as 

 organs of attachment, he adds the observation that the cirri serve as organs 

 of touch, and very probably test the surface to which they attach themselves. 

 In any case they, like the pinnules, are distinguished by their reflex irritabi- 

 lity. Even the larvse are very sensitive. Strong mechanical, electrical, 

 thermal, or chemical stimuli directly applied to the stalk easily cause the 

 breaking off of the distal part of the rays. The pieces broken off do not 

 merely, as Krukenberg reported, retain their reflex irritability for several 

 hours, but rather for days. The irradiation of stimuli is clearly affected in 

 Crinoids by very slight lesions ; they are very sensitive to elevations of 

 temperature. 



With regard to the movements of escape made by star-fishes and 

 brittle-stars, Prof. Preyer is unable to accept the exactness of the results 

 of Mr. Romanes and Prof. Ewart. He does not find that they try to escape 

 from the stimulus in a straight line, nor that if two neighbouring rays are 

 excited the line of escape is the " diagonal," nor that if the tips of five rays 

 are simultaneously excited there is a tendency to rotate round the vertical 

 axis. When a caoutchouc ring was firmly placed round two rays of Astropecten 

 pentacanthus there was no attempt made to escape, but after six days the 

 rays were broken off. After rapid and strong compression of a ray of 

 Ophioderma [Ophiura'] it was not withdrawn every time, but was often moved 

 in pendulum fashion without any attempt to escape. The answering move- 

 ments of Echinoderms are much more complicated than appears at first 



* Zool. Aiizeig., X. (1887) pp. 363-4. 



t MT. Zool. Stat. Neapel, vii. (1887) pp. 191-233 (1 pi.). 



