The Development of Scyphomedusae. 251 



But aside from physiological objections, abundant facts of 

 morphology go to discredit the assumption. Not to suggest 

 such a priori reasons as that out of the large number of scyphis- 

 tomal tentacles only eight, or in some cases four, should be thus 

 modified, it may be worth while to call attention to the more 

 significant fact that medusae are well known whose development 

 is direct, and consequently have no scyphistomal tentacles from 

 which rhopalia might be developed. Nor does it suflice to say that 

 in such cases heredity may have established the condition. But 

 other facts are significant. In the case of polydisc strobila only 

 the primary ephyra as a rule has had the requisite tentacle prim- 

 ordium for such transformation; others of the series should be 

 found to lack sensory bodies, if the assumption be vahd. But of 

 course this is not the case. Furthermore, as already intimated, 

 during the experiments on regeneration referred to there was not 

 the slightest evidence that any tentacular primordium was neces- 

 sary, or in the slightest degree concerned in the process. As is 

 well known, it is not rare in such experiments to find appearing 

 some heteromorphic organ arising in the course, such as the occur- 

 rence of a tentacle instead of an eye (crustacea) . Not the slightest 

 evidence of the sort was found in the case under consideration. 

 As may be noted (op. cit.), regeneration proceeded directly from 

 the entoderm of the marginal pockets, or rarely from other por- 

 tions of the margin. It was also practicable to trace step by step 

 the histogeny of the organs from start to finish. 



This view is supported also by other observers. Bigelow 

 (1900), pointed out that in Cassiopea the rhopalia arose prior 

 to the atrophy of the tentacles; and Friedemann (1902), p. 264, 

 says explicitly that the sense bodies are not transformed tentacles. 

 These observations go to confirm the earlier view of Goette (1887), 

 that the sense organ can not be considered as homplogous witJi 

 the tentacle of the scyphistoma. 



We seem to have here another illustration of the baleful con- 

 sequences of uncritical subservience to theory. It may be doubted 

 if in the original hypothesis any attempt of a critical character 

 was made to work out the primary genesis of the organs in question. 

 To the time of the above mentioned experiments the writer has 



