PREVIOUS INTERPRETATIONS OF CNIDARIA 181 



septa, really grow from the outside inwards. Yet these two 

 forms are two completely different things if viewed from the 

 standpoint of the comparative morphology, as well as that of 

 physiology. In both cases, in Turbellaria as well as in Cnidaria, 

 a vascularization of the periphery takes place by means of 

 which fluid food can be brought to any part of body. The 

 experts in Turbellaria are inclined to accept such an interpreta- 

 tion. The middle layer contains powerful strings of muscular 

 tissue; some experts in Turbellaria, particularly O. Steinbock 

 (1924:495-502), think that these strings of muscles that usually 

 extend dorsoventrally have a major role in the formation of 

 intestinal lobes and of intestinal diverticula, much as the sex 

 apparatus dominates the middle part of the posterior half of 

 the body. Yet the tendancy of the intestine to form diverticula 

 is not mentioned in this connection. I beUeve it probable that 

 here the intestinal waU has an active role, pressing forward 

 the diverticula into the tentacles as can be observed in some 

 species, or into some other excrescences, as can be obser- 

 ved in the species belonging to the genus Thjsano^^oon. It is pos- 

 sible that the strings of muscles that extend in the dorsoventral 

 direction were developed later or almost simultaneously with 

 the formation of diverticula. Obviously, we have to distinguish 

 between the formation of limbs and intestinal diverticula. 



A progressive trend can be observed in the evolution 

 of sarcosepta in the primarily solitary anthopolyps. A strong, 

 locally developed system of longitudinal muscles has been 

 developed in their interior; these muscles can be observed in 

 transverse sections as the well-known flags of muscles. Be- 

 sides these muscles other, weaker, muscular systems have also 

 been developed which extend in other directions. Gonads are 

 transferred into the mesenchyme of sarcosepta (frequently 

 into certain pairs of septa only) which has influenced scholars 

 so that they have begun to speak about entodermal gonads 

 (Endocarpa), similarly as in the Ctenophora: gonads, however, 

 should not be attributed to any body layer. A special histolo- 

 gic-cytological differentiation took place in the free margins of 

 13 



