142 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



twelve segments was pointed out by Brown, and was also noted in the 

 older papers of Ehrenberg and Romanes. 



According to Romanes, monstrous forms of Aurelia aurita are of fre- 

 quent occurrence. Abnormality consisted in multiplicity and abortion 

 of parts. All cases of asj'mmetrical multiplication applied to litho- 

 cysts, and always occurred in the same manner. When there were nine 

 instead of eight lithocysts, the extra one was always fully developed 

 and in close proximity to one of the normal lithocysts. 



In symmetrical abnormalities all parts of the organism were equally 

 affected. Thus all examples of multiplication extended proportionally 

 to ovaries, nutritive canals, lithocysts, and tentacles, the effect being to 

 increase the number while adhering to the type of the natural segments. 

 In all cases the degree of abnormality was the same; e. g. 6 ovaries, 

 24 unbranched radial tubes, 12 lithocysts, and a six-lobed manubrium. 

 All parts and segments thus increased one third their normal number. 

 Romanes calls attention to the fact that this is the same proportional 

 increase as in Sarsia, with six canals, and explains it as accidental. 

 Supernumerary lithocysts always occur at the ends of the faintly 

 colored radial tubes, never at the ends of the darker ones. 



Segments and lobes of the manubrium may be multiplied without the 

 ovaries increasing in number. Again, segments may multiply and manu- 

 brium and ovaries remain normal. Processes of multiplication may not 

 extend to all quadrants of the umbrella. Multiplication of parts may 

 be confined to one side of the umbrella, thus doubling or tripling organs 

 on one side only. 



Abnormalities usually are symmetrical. When they are not, the 

 manubrium and ovaries are not affected, the segments only being multi- 

 plied. Abortion of parts takes place in the same symmetrical way 

 as multiplication : there may be one ovary and six segments, and three 

 ovaries instead of eight and four. Segments and ovaries may also be 

 reduced to one half the normal number. In these two cases the 

 manubrium is not affected. Abortion of parts was observed in the 

 ovaries only. Partial suppression of ovaries was of frequent occurrence. 

 The most prevalent case was where one ovary was smaller than the other 

 three. Reduction also occurs in two alternating ovaries (i. e. opposite 1). 

 Sometimes three adjacent ovaries were reduced in size. 



Total suppression of one ovary was more rare. Only in twelve cases 

 in thousands was total suppression of two ovaries observed : some- 

 times it was two adjacent ones, and more frequently the two opposite 

 ones that were absent. In one case three ovaries were absent, the 



