584 MR. E. A. MINCHIN ON THE ATTACHMENT [NoV. 19, 



capsules, such as are represented in figures 3, 4, and 5, the walls 

 are relatively thick, containing a great deal of mesogl(Ea, and the 

 capsules themselves open by a comparatively wide opening into the 

 lumen of the groove. In the larger capsules, on the other hand 

 (figure 6), the mesoglcea is scarcely visible, appearing as if squeezed 

 out by the pressure of the numerous embryos contained in the 

 capsules, and their openings are much narrowed. They always 

 contain embryos in all stages of development, from segmenting ova to 

 fully-formed planulse. In the series of sections from which figures 3, 

 4, and 5 were drawn, several ova were found of only four or eight 

 segments. In addition to the embryos contained in the brood- 

 capsules, a great number are always to be found free iu the bottom 

 of the groove or lodged in the foldings of its margin. 



My excuse for publishing these details is that after I had made 

 out the structure of the pouches from my sections, 1 consulted the 

 numerous works on the anatomy and embryology of Aurelia, and 

 found the brood-capsules quite erroneously described by Clans and 

 Agassiz ; while in other writers I have found no mention of them 

 at all. 



Claus (' Untersuchungen iiber die Organisation und Entwicklung 

 der Medusen,' Prag, 1883) writes : — " The ova pass from the ovary 

 into the gastric cavity and through the mouth between the apposed 

 surfaces of the arms, where, surrounded by a slimy excretory 

 product of the endoderm (von einer schleimigen Absonderungs- 

 masse des Entoderms umhiillt), they run through their embryonic 

 development up to the swarming planula, as if in a brood-cavity." I 

 find this account to be incorrect, as far as my specimens go. 



Agassiz (' Contributions to the Natural History of the United 

 States,' vol. iv.) states (pp. 14 and 15) that the embryos of Aurelia 

 jiavidula leave the ovary as small ciliated larvae, either globular or 

 oval in shape, and tcith distinct inner and outer wuUs^ ; in this 

 condition they reach the pouches. In another passage (p. 58) he 

 says : — " The ovaries .... discharge their eggs into the cavity above 

 that floor [i. e. of the genital sacs], from which they have no other 

 escape than through the channels leading into the main cavity of 

 the body, from which they pass along the medial canals of the 

 amis into the pouches formed by the foldings of their margin}^, 

 ■where they undergo their first development." In figure 9 of his 

 plate viii. he represents some of the pouches containing "eggs and 

 planulse." Speaking of Cyanea, he says: — "The eggs of Cyanea 

 are able to lodge between the plications of the inner surface of the 

 actiuostome, though not provided with special pouches as in Aurelia" 

 Thus Agassiz clearly recognized the fact that the embryos of Aurelia 

 are carried in special pouches ; but he wrongly descrihes their 

 formation as foldings of the margin of the arm ; and, moreover, he 

 states that the embryos do not reach them till they have attained 

 the planula condition. If this is the case in Aurelia Jiavidula, it 

 certainly is not so in A. aurita. I have succeeded in finding in the 

 pouches embryos in all the stages described and figured by Claus 

 ' The italics are not Agassiz's. 



