Budding begins as a slight protrusion of the basal ] 

 nosarc) of the colony, which then becomes spherical 

 club-shaped, as in Fig. 51, until it assumes the form 

 It remains permanently attached in all the Hydroic 



species of Tubularia the heads of the zooids successiv 



Multiplication by fission has only been observed in 



In this the pendent stomach divided iu two, becomi 

 which was followed by a vertical division of the urn 



animals, includiuu: tin* mammals. The germ elongates ami finally 

 escapes from the ovisac (gonophore) of the parent as a ciliated 

 "planula," a term first applied to it by Dalyell. 



Now how do these planulas become converted into hydras, and 

 through them into medusa?? A glance at the accompanying figures 

 will give the main points in the life history of a not uncommon 

 Hvdroid found on our shores, a Melicertum allied to Campanu- 

 la! ia (Fig. 62). We are indebted to Mr. A. Agassiz (Seaside 

 Studies in Natural History) for the following facts and illustra- 

 tions regarding its history. After keeping a number of the Meli- 

 certum in a large glass jar for a couple of clays at the time of 

 spawning, he found that the ovaries, at first filled with eggs, 

 brcame emptied, and that the planula?, at first spherical and after- 

 wards pear-shaped (Fig. 59) swam near the bottom of the jar, and 

 soon attached themselves by the larger end to the bottom of the 

 jar (Fig. 60). "Thus their Hydroid life begins; they elongate 

 gradually, the horny sheath is formed around them, tentacles 

 arise on the upper end, short and stunted at first, but tapering 

 rapidly out into fine, flexible feelers; the stem branches, and we 

 have a little Hydroid community (Fig. 61), upon which, in the 

 course of the following spring, the reproductive calycles contain- 

 ing the medusa? buds will be developed." 



