564 Chas. W. Hargitt. 



variations in Aurelia, Bateson examined 1763 adult specimens 

 taken on the Northumberland coast in 1892. In the tabulation 

 of his results he presents details of only the gonads and oral lobes. 

 Of these there were but 28 abnormal specimens, or a variation of 

 only 1.6 per cent. Of the 28 abnormal individuals 19 he considers 

 as "symmetrical varieties," and observes that the other 9 speci- 

 mens, or 33 per cent are "irregular varieties" and are seen "for 

 the most part in single specimens only." Here Bateson apparently 

 falls into the same error which he has criticized in Romanes, 

 namely, the attempt to reduce the variations to "symmetrical 

 varieties," regarding "irregular varieties" as exceptional. But 

 the presence of 33 per cent of the so-called "irregular varieties" 

 is too large a proportion to be designated as exceptions. 



As is well known Aurelia is an octamerous medusa, each octo- 

 mere being characterized by a single, more or less dichotomously 

 branched radial canal, at the terminus of the central stem of which 

 is located the sensory body, or rhopalium, and separated from 

 the adjacent octomere by an unbranched canal, as shown in 

 several of the diagrams. In normal individuals this arrangement 

 is very symmetrical, and easily distinguishable. It must not be 

 inferred, however, that the several branching canals are exactly 

 similar, or symmetrical. Indeed it may be safely said that 

 probably no two in a given individual are exactly alike, any more 

 than are two leaves of a given plant. Still, the differences are 

 usually slight, striking variations occurring chiefly in those cases 

 where departures from the typical arrangement are considerable. 

 For convenience in following readily the subsequent discussions, 

 it may be well to briefly remind the reader that for descriptive 

 purposes the several canals have been designated by the special 

 names, perradiai, signifying those canals arising between the 

 gastric pouches, or mouth angles; mterradial, indicating those 

 occupying intermediate positions, or emerging from the outer 

 median portion of the gastric pouches; while the term adradial 

 refers to the unbranched canals alternating with the other two 

 series. 



Gastric and Reproductive Organs. 



Among the most conspicuous variations from the typical con- 

 dition just described are those involving a numerical, or meristic 

 departure. This will be readily understood when it is remembered 



