ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 251 



strating the phyletic migration of tte maturation-point in the Euco- 

 pidaB ; this it was necessary to do unless the position of their gonads 

 could be allowed to contradict the views of Weismann that the 

 primitive position of the germ-cells was the ectoderm of the manu- 

 brium of the free MedusBB. 



Hydroid Phase of Limnocodium Sowerbii.* — A. G. Bourne now 

 describes the organism which he found | on the root filaments of 

 Pontederia, and which in its mode of growth somewhat resembles an 

 encrusting sponge. The smallest pieces are mere knobs, the largest 

 are produced into three or four lobes, about 1/8 in. long. No 

 tentacles were seen, but they may develope subsequently ; there is no 

 trace of a true perisarc; the organism does not exhibit any active 

 movement, but throws off nematocysts, when irritated ; in preserved 

 specimens there is only a very minute lumen, leading from the 

 terminal aperture. The endoderm cells near the apex are peculiarly 

 arranged, and "somewhat suggest in appearance the rudiment of a 

 sub-umbrella found in such forms as Hydractinia " ; in the basal 

 region the endodermic cells are normal, and the cavity is well 

 developed. 



The author briefly notes the appearance of structures resembling 

 buds formed by the medusiform persons; and gives a history of 

 Limnocodium up to date. It is suggested that the Medusa did not 

 establish itself at Kew because there was no Pontederia in the tank. 

 " In dealing with the hydroid form here described, we must remember 

 that Limnocodium is undoubtedly one of the Trachomedusfe. No 

 trachyline form has before this been shown to be connected with any 

 hydroid condition, but we know less about the Trachomedusse than 

 about the Medusas derived from Gymnoblastic or Calyptoblastic 

 hydroids. Direct development has been shown to occur in two or 

 three genera of the Trachylinse (^Geryonia &c.), whereas regarding the 

 life-cycle of the other forms we know nothing. The hydroid here 

 described is now in an immature condition. It may be a creepinp' 

 stolon, which when further developed will resemble the hydroids • it 

 may turn out not to be comparable to other hydroids, and to be a 

 fixed sporosac of some kind; but if it grows into an adult form 

 resembling the form at present known, it may serve as the type of a 

 new group of hydroids related to the Trachyline Medusoids." 



Life-history of Eutima mira.J — W. K. Brooks has reared the 

 hydroid of Eutima mira from the egg. In the transparent pear-shaped 

 planula the delamination of the entoderm from the inner ends of the 

 ectoderm-cells takes place most rapidly at the small end, but ento- 

 derm-cells are formed over the whole inner surface. 



After the entoderm is formed, the small end of the planula 

 becomes elongated, and the entoderm is invaginated. The ventral 

 surface of the small end is soon fastened to some solid substance, and 

 the invaginated portion is protruded and pours out its cement. After 



* Proc. Eoy. Soc, xxxviii. (1884) pp. 9-14 (1 fig.). 



t See this Journal, ante, p. 72. 



j Zool. Anzeig., vii. (1884) pp. 709-11. 



