1889.J OF THE EMBRYOS IN AURELIA. 585 



{loc. cit.), from segmenting ova to the fully formed planulse or 

 "clistogastrulse." 



Other Medusae belonging to the Acraspeda carry their ova about 

 during the first stages of development. Von Lendenfeld states (Proc. 

 Linn. Soc. N. S, Wales, vol. ix.) that in Pseudorhiza " the embryos 

 are carried about in pouches suspended in great number from the 

 radial canals which rvm centripetallj' from the ring-canal. They 

 remain there till tliey are fit to turn into young Scvphistomes." In 

 Sfylorhisa {Phyllorhiza) punctata, he says (/oc. c?^), " the young 

 embryos adhere to the mother's filaments until the3' have nearly 

 attained the Scyphistoma stage." The same author describes 

 (' Zeitschrift fiir wiss. Zoologie,' 1888, p. 301) in Cyanea anasJaila 

 and Phyllorhiza punctata a peculiar arrangement of filaments on 

 the underside of the arms, by which the embryos appear to be 

 nourished. 



P.S., Dec. 9, 1889. — Since writing this article my attention has 

 been directed to Ehrenberg's paper, "Ueber die Akalephen des rothen 

 Meeresund den Organismus derMedusen derOstsee" (Phys. Abhancll. 

 Akad. Berlin, 1835). Ehrenberg gives a rough figure of Aurelia 

 aurita showing a magnified external view of the pouches and their 

 contained embryos (Taf. viii. fig. 1, and Taf. iii. fig. 1) ; and states 

 (p. 197), first, that the brood-pouches are either formed by tlie 

 pressure of the " Kugeln " {i. e. ova and embryos) which collect in 

 the groove of the arms, or else are preformed by the mother for 

 their reception ; secondly, that the pouches increase in size as more 

 embryos crowd in ; and thirdly, that when the embryos quit the 

 pouches the latter collapse and disappear. 



EXPLANATION OF PLATES LVII. & LVIII. 



In all the figures ect denotes the ectoderm ; mcs, the mesogloea ; end, the 

 endoderm ; d, digitellffi; aud the letter G is placed in the lumen of the groove 

 of the arms. 



Fig. 1. An oral arm of Aurelia aurita, covered with the little pouches con- 

 taining embryos. The letter in is placed in the cavity of the mouth. 



2. A transverse section of an oral arm -nhich was entirely without brood- 



pouches. The numerous jjlications are due to the arm having been 

 crumpled while preserved in spirit. 



3. A transverse section of an arm which had few and somewhat small 



pouches, a and b, two of the pouches containing embryos. 



4 & 5. Two more sections through the pouches lettered a and h in the 

 last figure. 



6. A transverse section through an arm which had numerous and very 

 large brood-pouches. Only one side of the section is drawn, c, d, e, 

 and /, four pouches, each containing a great number of embryos, 

 those in c, d, and / being only represented in outline. 



Proc. Zool. Soc— 1889, No. XXXIX. 39 



