192 MR. G. J. EOMAJSTES ON SOME NEW SPECIES, 



which is here represented in fig. 7 (PI. XY.). It will be seen that all 

 parts of the organism have undergone multiplication in a common 

 ratio ; so that the effect is to " increase the number whilst adhering 

 to the t;i/pe of the natural segments above alluded to," and this 

 without in the least degree destroying the general symmetry of the 

 animal. In such cases the manubrium is usually six-lobed. 

 In other cases, however, some one or more of the normal seg- 

 ments do not take part in the multiplication ; so that while the 

 number of segments are increased and their natural type con- 

 formed to, the animal nevertheless, as a whole, becomes asymme- 

 trical. Of such a case fig. 8 (PI. XV.) may be taken as an example. 

 It will be observed that in the last figured specimen the ovaries 

 were not afiected by the process of multiplication, although 

 this had aflJected both the manubrium and the segments of the um- 

 bella. Such an immunity from the abnormal process in question 

 is frequently presented, both by the ovaries and by the manubrium, 

 even in cases where it has affected the umbrella to a large extent. 

 This may be seen in fig. 9 (PI. XV.), where it is also worth w^hile to 

 observe the eymmetrical manner in which the multiplying process 

 has affected the umbrella regarded as a whole. In fig. 1 (PI. XVI.) 

 we have an exactly similar case, except that the multiplying process 

 has failed to extend to one of the quadrants of the umbrella. 



In some cases the multiplication of parts takes place on one side 

 of the umbrella only, as may be seen in figs. 2 and 3 (PL XVI.). In 

 thefirst of these specimens one of the ovaries has become duplicated; 

 and all the other parts in its segment having done the same, the 

 manubrium presented five lobes, and the umbrella ten segments. 

 In fig. 8 one of the ovaries has become tripled ; and the other parts 

 of the umbrella being multiplied in the same manner, the total 

 number of segments is twelve. The manubrium, however, in this 

 case only presented the same number of lobes as in the last one. 

 Abortion of parts in Aurelia takes place in the same symme- 

 trical way as does multiplication of parts. For instance, in fig. 4 

 (PI. XVI.) it is observable that one ovary is absent, while the 

 segments of the umbrella are reduced to six. Similarly, in fig. 5 

 (PL XVI.) the ovaries and segments of the umbrella are reduced 

 to one half of the normal number. In neither of these specimens, 

 however, was the manubrium affected by the reducing process. 



I have now given a sufficient number of illustrations to render 

 an accurate idea of the various ways in which the normal type of 

 Aurelia is seen to be modified by the multiplication and the sup- 

 pression of parts. The most remarkable point with regard to 



