AND MONSTttOUS FOKMS OF MEDUSAE. 529 



and lithocysts. In particular, there are 16 principal radial tubes 

 tliat proceed, in straight lines and without brandling, from the 

 centre to the circumference of the umbrella. Of the 16 tubes, 

 one passes directly to each of the eight lithocysts, while the 

 remaining eight tubes alternate with these. Thus the 16 radial 

 tubes together mark out, as it were, the whole umbrella into 16 

 equal segments. Well, in all the examples which fell under my 

 notice of abnormal multiplication of parts in Aurelia (other than 

 those of mere duplication of lithocysts), the precise and peculiar 

 symmetry just described was strictly adhered to : in all these 

 examples the undue multiplication extended proportionally to 

 ovaries, nutritive tubes, lithocysts, and tentacles ; so that its 

 effect was to increase the numher while adhering to the type of 

 the natural segments above alluded to. It is further remarkable 

 that in all the instances I met with, the degree of abnormal multi- 

 plication was the same ; for in all the instances the ovaries were 

 6, the principal or unbranched radial tubes 24, and the lithocysts 

 12. All the parts, and therefore all the natural segments, were 

 thus in all the observed instances increased by one third of their 

 normal number. It is curious to note that we have here the same 

 proportional increase as that which has already been described in 

 the case of Sarsia. This, of course, is probably a mere accident ; 

 but whether or not it is so, I think that, as there is certainly no 

 reason either in the ease of Sarsia or of Aurelia to regard the 

 forms in question as distinct species, it becomes worth while to 

 draw attention to the very deiinite manner in which the abnormal 

 multiplication of parts seems always to occur in these, the only 

 genera of Medusae in which such multiplication has as yet been 

 observed. It is, perhaps, also worth while to add that in all the 

 cases where I noticed this undue multiplication of parts, both in 

 Sarsia and in Aurelia, the animals were remarkable for the un- 

 usual amount of nervous energy which they displayed. There 

 can be no doubt that this fact is to be attributed to the unusually 

 large supply of nervous matter that was secured to the organism 

 by the multiplication of its marginal bodies. 



As regards abortion of parts in A. aurita, I cannot say that I 

 liave ever observed this to occur in any organs other than the 

 ovaries. In these, however, suppression to a greater or less 

 extent is of pretty frequent occurrence. Most usual is the case 

 where one of the four ovaries is of smaller size than the other 

 three. Often the abnormal diminution extends to two altcrnato 



LINN. JOURN. — ZOOLOGY, TOL. XTI. 38 



