70 EMHRYOLOGY 



outer ectoderm mesoglcea has been secreted. In general 

 the development of the nectocalyx is quite like the budding 

 of a Hjdromedusa described above (p. 43). On the funda- 

 ment of the tentacle {t) the individual nettling tubercles 

 can be seen developing as secondary evaginations (Fig. 'SO C). 

 The further changes (Fig. 31) consist in a considerable 

 enlargement of the first nectocalyx, which now, after the 

 ]-eduction of the nuti-itive cells, is the most voluminous 

 structure of the young colony. The polypite (po) now 

 acquires its permanent structure by the breaking through of 

 the mouth at its distal end, while the teiitacle (t), in this 

 case persisting (not larval), attains its complete develop- 

 ment. Of interest is the appearance of new buds on the 

 rudiment of the stem, first of all that of a hydrophillium 

 (Fig. 31 hp]i), with the development of which is established 

 the first group of individuals (cormidium) of the subse- 

 quently elongated stem — consisting of a polypite, a dactylo- 

 zooid, and hydrophillium — which is afterwai-ds developed into 

 the Eudoxia. At the same time we see two smaller buds 

 arising, one of which must be considered as the second 

 nectocalyx (Fig. 31 7/c), whereas from the other the elements 

 of the second group of individuals of the stem bud forth. 



In the stage Fig. 30 li, which in Fig. 30 C and Fig. 31 undergoes its 

 further development, is shown a larval stage exceedingly characteristic 

 of the Calycophoridffi, which has been designated by Haeckel as the 

 Ciilyconula, and which rej^resents essentially the SipUoinila-stage of the 

 CalycophurnUc. Haeckel (No. 70) regards this stage as an individual of 

 the second degree (iDerson), and recognizes in its component parts the 

 constituent organs of an Anthomedusa, which here present a remark- 

 able dislocation. For if the nectocalyx corresponds to the umbrella and 

 the polypite to the manubrium of the medusa, then it is evident that the 

 l^olypite is here attached to the ex-umbrellar side of the medusa-bell. 

 Haeckel explains this dislocation by the assumption of a ventral fissure 

 in the umbrella of the ancestral forms, through which a gradual emigra- 

 tion of the manubrium was possible. Furthermore the only marginal 

 tentacle of the medusa present has moved from the margin of the 

 nectocalyx to the base of the jtolypitc. 



The assumption that the Siphonula thus characterized actually corre- 

 sponds to an ancestral form acquires an apparent support from the 

 circumstance that the same type of form is found again in the groups of 

 individuals of the stem (cormidi(i). For the individuals of the stem in 



