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PROCEEDINGS OF THE 



[Dec, 1856. 



original pair, so that the larva is next provided with four perfectly 

 similar tentacula. Fig. 25, PL 6, is a larva at this stage of devel- 

 opment. It is now a perfect hydra, differing in nothing from other 

 four armed hydras, except in the proportion of parts in which they 

 differ among themselves. The proboscis is excessively long, three, 

 or four, or five times the length of the body, and very extensible, 

 while that which represents the stem-end of the Tubularian larva 

 is almost null, gradually, however, acquiring a greater protuber- 

 ance, never for the purpose of forming a stem or other organ of 

 attachment, (for the present larva never fixes itself,) but simply to 

 produce the rounded dorsal surface of the future Medusa. This is 

 the earliest stage at which I have observed a phenomenon, doubt- 

 less one of the most singular in the economy of this singular 

 Medusa. I allude to the circumstance that the larva derives its 

 nourishment from the body of the parent by introducing its elon- 

 gated proboscidian scyphon into her mouth, and so sucking out, by 

 ciliary action, the mixed water and chyme prepared in the stomach. 

 PI. 5, fig. 28b, exhibits three larvae of different stages, with their 

 proboscides so introduced. This, as first stated, is the earliest 

 stage at which I have observed the phenomenon, and the latest is 

 exhibited in the larva marked a, in the same figure. It doubtless, 

 however, is the only mode of obtaining food with which they are 

 provided, and probably will be found in operation from the time 

 that the mouth is formed in the bi-tentaculate stage, to that period 

 hereafter to be described, when the medusa-disk nearly complete 

 enough for swimming, the shortening of the proboscis, which takes 

 place at this time, prevents its being protruded so far as to servf 

 the purpose of a sunction tube. After the parent has devoured 

 some small animal, (which in every instance I have been able 

 to observe was a small Crustacean,) and after digestion has so far 

 proceeded that the hard parts are ready to be regurgitated, I have 

 seen the process going on, and, on one occasion, regurgitation 

 taking place, one of the larvse, at the same time withdrawing its 

 proboscis, was seen apparently endeavoring to catch with open 

 mouth some of the few smaller floating particles vomited out with 

 the empty limbs of the Crustacean. But this is the only occasion 

 on which I have ever certainly seen the larva attempting to take 

 food without having its own mouth within that of the mother. 

 Also, the proboscides, are observed, all introduced at times when it 

 is impossible to be seen that there is any fresh food in the stomach 

 of the parent. But during this larvigerous period an examination 



