238 



ACTINIARIA 



In the third pairs of the third cycle the weakest mesentery is facing the second pair of the second cycle (designated 

 with II a, a II). The mesenteries of the third order thus seems to be developed according to the Actinostola- 

 rule. Regarding the insertions of the mesenteries of the second cycle on the pedal disc, we find that also here 

 the Actinostola-iule is valid. The weakest mesentery in each pair namely stands next to the mesenteries of 

 the first order. Thus the Actinostola-rule appears earlier here than in the genus Actinostola, where it is only 



t to be distinctly observed from the third cycle. The 



cause of this difference is that in Stomphia, provided 

 with 18 pairs of perfect mesenteries, the number of pairs 

 of mesenteries of the second cycle probably is doubled (12 

 instead 6), while in Actinostola the number is the typical 

 6. It is easy to understand that the mesenteries of the 

 second order in a species with only six pairs of second 

 mesenteries cannot be arranged according to the Actino- 

 stcla-Tule. For that arrangement a reduplication of these 

 mesenteries is first of all required. 



The specimen of which I have above described 

 and reproduced the arrangement of the mesenteries, 

 was of rather considerable size (the height was about 

 2,5 cm and the breadth of the pedal disc 6 cm in pre- 

 served state). The number of the tentacles was 74 and 

 the mesenteries consisting of no less than 140 paired 



and 72 unpaired mesenteries. Also the mesenteries of 

 the fourth cycle and those of the following are arranged 



Textfig. 210. Stomphia coccinea. 



Diagram of the arrangement of the mesenteries. The spaced- 

 out lines indicate the extension of the stronger mesenteries 

 on the pedal disc. The fertile mesenteries are provided with 

 groups of points on the inner side. The arrows in the in- 

 terior of the diagram indicate the place of the weaker according to the Actinoslola-Tule, sometimes a mesen- 



mesentery in the pairs of the third cycle. tery of a subsequent cycle is established, before the 



mesentery of the preceding cycle has got its partner. As this mesentery is developed on the side away from 

 the longitudinal muscles of the hitherto unpaired mesentery of the preceding cycles, the arrangement of the 

 mesenteries seems apparently to be contrary tothe/lcfo'wos/o/#-rule. Two unpaired mesenteries of two different 

 cycles (6 and 7) in such a case are placed beside each other. The greater part of the mesenteries are developed 

 only in the most proximal part of the body at the limbus and mostly appear as small folds without filaments 

 (in the textfigure these mesenteries are marked with stippled lines). 



Issuing from the one directive pair (i fig. 210) the arrangement of the mesenteries in the more 

 closely examined specimens was as follows. The fertile mesenteries are marked with k ; (k) indicates that only 

 the strongest mesentery of the pair is fertile ; o signifies unpaired mesentery not having got its partner. The 

 perfect mesenteries are designated with Roman numerals, the imperfect with common numerals. 



t k t (k) k (k) (k) k k k k (k) k 



1654535456 11654535456 II 6 5453 5 45 6 1654535456 II 654 



00 00 00 00 00 



