72 SUMMARY OF CURRENT RESEARCHES RELATING TO 



edges of the grooves of only one of the eight primary arms are fused 

 at their point of bifurcation, and it is the same arm that alone has a 

 nematophoro; P. haeckclii has, therefore, undergone degeneration, 

 and is, consequently, a form which is phylogenotically younger than 

 P. aitrosa. The new species difters from all known acraspcdoto 

 Medustc in that it cannot bo divided either into two congruent or two 

 synmiotrical halves. It is further remarkable for being commensal 

 with a fish — Enoplosns armatus. 



Development of the Versuridae.* — The family of the Versuridaa, 

 comprising large rhizostomous Medusa), is comparatively rare in the 

 northern hemisphere, and their development has only recently been 

 described by Claus, who studied the Mediterranean CotylorMza ; t 

 E. V. Lendeufeld, having obtained several young stages of the 

 spotted brown blubber which he has named PhijllovMza punctata, 

 has found its development to differ from anything observed hitherto. 

 The eight marginal bodies (organs of sense) in the principal radii 

 of the first and second order exist in the young larva. But besides 

 these, the larva possesses a greater number of similar marginal 

 bodies, which become less in number with increasing age. First 

 there arc 24, then 16, and finally 8. But the umbrella margin 

 retains the power of producing marginal bodies ; and if after an 

 injury of the margin new margin-flaps are formed, marginal bodies 

 are also produced between them. The character of the embryonic 

 tissue to form marginal bodies between all flaps, again makes its 

 appearance if a new formation of the umbrella margin takes place. 



Flexor Muscle of the Hydroid Polyp of Sarsia radiata.i— R. v. 

 Lendenfeld gives an account inter alia of the muscular mechanism 

 by means of which the hydroids of this Sarsia (n. sp.) perform 

 their constant flexions, often through nearly 180°, so as to lie along 

 the hydrocaulus. This characteristic bending takes i^lace uniformly 

 at one spot, namely, where the hydranth passes into the hydrocaulus 

 and where the hydrocaulus-perisarc ends obliquely truncated. Sec- 

 tions show a bundle of longitudinal muscle-fibrils, lying peripherally 

 to the supporting lamella. This muscle Dr. von Lendenfeld calls 

 the flexor. The fibrils of the muscle proper, which show an irregular 

 radial striation, embrace longitudinal folds of the supporting lamella, 

 and are strictly comparable with those of Siphonophora and of the 

 craspedote Medusse, as described by the brothers Hertwig. 



Hydriform Phase of Limnocodium Sowerbii.§ — For more than 

 four years the origin of the fresh-water jelly-fish, Limnocodium 

 Sowerhii, in the Eoyal Botanic Gardens, Eegent's Park, has been 

 involved in obscurity, and during that time the tank has been cleaned 

 out more than once. Frequent observations revealed no clue to the 

 mystery, though it was of course certain that the contents of the tank 

 must ultimately furnish it. 



A more minute search was made by Prof. Lankester and Mr. A. G. 

 Bourne on the occasion of the cleaning of the tank at the end of 



* Pioc. Linn. Soc. N. S. Wales, ix. (1884) pp. 307-9 (1 pi.). 



t See this Journal, iv. (1884) p. 391. 



J Zool. Anzeig., vii. (1884) pp. 584-91. 



§ Nature, xxxi, (1884) p. 107. 



