MEDUSA BIFIDA. 127 



A vigorous subject attached to a fragment of shell on March 27 is 

 represented, Plate XX. fig. 6 ; enlarged, fig. 7. The different strata of 

 Medusae are advancing rapidly to maturity : the bulb has attained the ge- 

 neral form of a hydra ; and its tentacula are extending with some regu- 

 larity. Though pendulous originally, the Medusan roll has assumed a pe- 

 culiar curvature, so that the most mature portion turns upwards. In 28 

 days longer, nothing of this subject but a vigorous and symmetrical hydra 

 remained, fig. 20, which in 15 more, had become the parent of others, 

 fig, 21 ; and in two months from the beginning, in March, its family had 

 increased to seven members, fig. 22. This parent, originally a bulb on 

 March 21, fed readily and copiously, and survived in fine condition 290 

 days from that date. 



Thus it is unquestionable that, wherever there is a roll of Medusae there 

 is also present a hydra sustaining it, which is developed in symmetry as 

 the Medusae escape. 



How this hydra comes to be present is a difficult question. Is it an 

 original hydra, whereof the tentacula are obliterated, and the body com- 

 pressed ? Has the roll been generated by that hydra, or is it a foreign 

 substance ? Is the body of the original hydra actually partitioned into a 

 number of Medusa, all except a portion at the base, developing as a new 

 hydra ? If any of these facts be admitted, it would be well to see its con- 

 firmation. My original impression was, that the body of the original 

 hydra still subsisted ; that it was disfigured, compressed, the tentacula ob- 

 scured, but that it recovered its shape. It is positive that, unless the bulb 

 be a new generation affixed to the end of the Medusan roll, that the whole 

 body of the hydra is not consumed and exhausted by the successive libe- 

 ration of the Medusae, for a portion becoming a symmetrical hydra is uni- 

 formly displayed from the point whereon the roll was generated, imposed, 

 or rested. 



It is unnecessary to recur to the history of the Medusa. Sometimes 

 an unnatural adhesion of two or more takes place in the embryonic roll, 

 from which they should be detached singly, in the regular course of its 

 dissolution ; and there are sometimes real monstrosities, as repeatedly oc- 

 curring among the lower tribes. 



