220 



ACTINIARIA 



Fig. 204 Fig. 205 



Textfigs. 204 — 205. Sicyonis variabilis. 

 Fig. 204: Longitudinal section of the apex of tentacles. 

 Fig. 205 : Transverse section of the base of a mesentery 

 with basilar muscles. 



The arrangement of the mesenteries recalls that 

 of S. ingolfi and tuherculata but is more irregular. In 

 order to ascertain it, I have examined one whole spec- 

 imen and half two specimens. The textfigure 206 .-1 , B 

 shows the arrangement of the mesenteries, each in one 

 half of two specimens, the textfigure 207 that of the 

 third specimen. In A and B all mesenteries have been 

 drawn, in textfigure 207 the fertile have been left out. 

 In the textfigure 206 ^4 the most weakly drawn mesenteries 

 are not provided with longitudinal pennons and re- 

 productive organs, but are certainly future, fertile me- 

 senteries, though the reproductive organs have not yet 

 been developed, owing to the small size of the spec- 

 imen (the height i cm, breadth 2,2 X 1,5 cm). These 

 mesenteries appear only in the most proximal part of 

 the body. I think that I have also in this species been 

 able to determine the mesenteries of the first cycle (I). If we examine the textfigures more narrowly, we 

 find that there are in A (in one half of the specimen) 26 stronger pairs of mesenteries, of which 7 pairs perfect 

 and 2 pairs consisting of one imperfect and one perfect mesentery, in B 23 sterile mesenteries, of which 11 

 pairs perfect and 4 pairs built up of imperfect and one perfect mesentery (on the other, not drawn half 10 

 pairs were perfect and 2 pairs made up of one imperfect and one perfect mesentery). In C (fig. 207) we see 

 on one side 21 pairs of sterile mesenteries, of which 9 perfect and 4 made up of one imperfect and one 

 perfect mesentery, on the other side 24 pair, of which 8 perfect and 5 pairs consisting of one perfect and one 

 imperfect mesentery. The arrangement of the mesenteries thus displays great differences, and the mesenteries 

 are not symmetrically grouped on both sides of the directives (compare B, C). Manifestly, a still greater 

 alteration in the time of appear- 

 ance of the pairs of the cycles 

 has taken place here than in 

 the other species, whereby some 

 pairs of mesenteries have been 

 checked in their development 

 or wholly suppressed. The per- 

 fect pairs of mesenteries are 

 among themselves a little un- 

 equally developed, which is seen 

 by their insertion on the pedal 

 disc (on the figure 207 designat- „ ^^ ^ ^. . ^.,. 



/ o Textfigs. 206 — 207. Sicyonis variabilis. 



ed with spaced out lines) . Also Diagram of the arrangement of the mesenteries. In fig. 207 only the sterile mesenteries 



have been drawn. 



