AEGINUEA. 79 



The differences between the three intermediate forms, A. myosura Haeckel, 

 A. grimaldii Maas, and A. weberi Maas, are more doubtful, inasmuch as the first 

 two, at least, were described from such fragmentary specimens that Maas 

 (: 04 c ) himself admits the possibility that some of the apparent differences 

 may be due to imperfect preservation. A. myosura, according to Haeckel's 

 ('81) account, appears to differ from the other two species in having eight of 

 the gastric pockets large and eight small, and he makes no mention of the 

 pigmentation, a character so striking and so permanent even in alcoholic 

 specimens that it could hardly have escaped him. His failure to mention 

 secondary tentacles cannot, however, be construed as indicating their absence, 

 on account of the condition of his material. 



Maas (: 05) cites as taxonomic characters separating A. grimaldii from A. 

 weberi, size, arrangement of the gonads, and presence or absence of a periph- 

 eral canal system. It seems to me, however, that in the present case none of 

 these are very significant. According to Maas (: 05) A. weberi is 35-45 mm. in 

 diameter ; A. grimaldii only 12 mm ; but his figure from the fresh specimen of 

 the latter, said to be life-size (: 04 c , pi. 3, fig. 19), measures 23.5 mm. in 

 diameter. This discrepancy may perhaps be explained by the fact that the 

 " Monaco " specimens were preserved with osmic acid, which almost invariably 

 shrinks Medusae considerably. Furthermore, there is no evidence to show that 

 even 23.5 mm. is the largest size attained by A. grimaldii. 



The gonads in A. grimaldii, of which a female only was observed, are 

 described as consisting of large eggs, irregularly scattered over the gastric 

 pockets, whereas in A. weberi (male), as in A. myosura (likewise male), the 

 sexual products are evenly distributed, but there is good reason to believe 

 that this is a sexual, not a specific difference, inasmuch as the two sexes 

 of Solmissus marshalli exhibit precisely the same divergence. 



The question of canals, said by Maas to be absent in A. grimahlii (: 04 c , 

 p. 40) but present in A. loeberi (: 05, p. 78), is less easily settled. His con- 

 clusion for A. grimaldii seems to be supported by good evidence, afforded 

 by the study of sections, but the occurrence of true canals in A. weberi 

 is more doubtful. According to his account, gained from sections of the 

 margin, the canal system is so nearly obliterated that no definite endothelial 

 layer is to be found, although there is an open lumen. His chief reason 

 for considering this lumen as normal and not an artifact, is its regular 

 occurrence (: 05, p. 79), but as the second possibility still exists. 

 it seems to me unwise to lay much stress on this supposed character 



