504 SCIENTIFIC RECORD FOR 1884. 



appearance — iu reality the resting spores or protected germs which con- 

 serve the life of the individual through the cold and storms of winter, 

 and awake very early in the spring time into new life, yet a continuance 

 only of the same existence which was seen a few months before nestling 

 into this winter's sleep. 



" If this is the ordinary course with these organisms there seems no 

 reason to regard them as serious causes of the pollution of our streams, 

 though violent freshets before this resting period is reached may tear 

 them to pieces, and their decay may give a temporary taint to the 

 water." {Proc. Acad. Nat. Sc, PMIa., 1884, pp. 28-30.) 



CCELENTEEATES, 



Polyps. 



Variation in corah. — The Astrangiacea (Madreporaria) have been stud- 

 ied by Mr. S. O. Kidley, and have been found to present striking indi- 

 vidual variations in characters which have been assumed to be constant 

 and employed for the detinition of generic or supergeneric groups. 

 Such variations atfect the columella, costse, and paliform lobes, and 

 characters depending on their modifications must be em])loyed with 

 great caution in the study of the Astrangiacea, "whatever may be the 

 v^alue for classification of the corresponding parts in the TurbinoliidsB 

 and Oculinidae." (Joiirn. Linn. 8oc. London, 2ool., xvii, pp. ."^OS-SOO. 1 

 pi ; J. B.M. ,S. (2) V. p. 73.) 



Acalephs. 



The hydriforni sta<je of Limnicodinm. — Notices have been i^ublished 

 in previous issues of these records" of ])rogress in zoology, of the re- 

 markable little freshwater Medusa, named Limnicodium Sowerbii, in 

 the Victoria tank of the Royal Botanic'Gardens in Regent's Park, Lon- 

 don. About four years and a half had elapsed since the discovery of 

 the mature form before the hydriform stage was discovered, although 

 assiduous search had been made for it. But, on the occasion of the clear- 

 ing out of the tank in December, 1884, more than usual thorough search 

 was instituted, and this was at length rewarded by the finding of the 

 hydra on some Pontedericc imported from South America several years 

 ago. Professor Laukester immediately comuiunicated a notice of the 

 discovery to the London Times and Mr. A. G. Bourne (who first de- 

 tected it) to Nati()-e (v. 31, p. 107, December 4, 1884). The details were 

 not jmblished in 1884. 



ECHINODEEMS. 



Origin of Echinoderms. 



The development of the germinal layers of Echinoderms has been 

 studied by Prof. E. Selenka. The cleavage of the Q^g, is said in general 

 terms to be regular, but really " pseudo-regular" in the Asterioids or 



