. Seaside studies in natural history. Marine animals. 76 MAHINE ANIMALS OP MASSACHUSETTS BAT. immense number of these animals, with which the sea actually swarms at times, when we know that as fast as they are dropped, and it takes but a few days to complete their de- velopment, they each begin the same process; so that in the course of a week or ten days one such Medusa, supposing it to have produced six buds only, will have given rise to forty-two Jelly-fishes, thirty-six of which may be equally prolific in the same short period. These Medusae budding thus, and swimming about, carrying their
. Seaside studies in natural history. Marine animals. 76 MAHINE ANIMALS OP MASSACHUSETTS BAT. immense number of these animals, with which the sea actually swarms at times, when we know that as fast as they are dropped, and it takes but a few days to complete their de- velopment, they each begin the same process; so that in the course of a week or ten days one such Medusa, supposing it to have produced six buds only, will have given rise to forty-two Jelly-fishes, thirty-six of which may be equally prolific in the same short period. These Medusae budding thus, and swimming about, carrying their young with them, bear such a close resem- blance to the floating communities of Hydroids formerly known as SiphonophorsB, that did we not know that some of them arise from Tubularians, it would be natural to associate them with the Siph'onophorse. Kg. lOT. Fig. 108. Narwmia. (Nanomia cara A. Ag.) The Nanomia (Mg. 115), our free floating Hydroid, consists, when first formed, of a single Hydra containing an oblong oil bubble (Fig. 107). The whole organization of such a Hydra is limited to a simple digestive cav- ity ; it has, in fact, but one organ, and one function, and consists of an alimentary sac resembling the proboscis of a Medusa (Fig. 107) ; the oil bubble is separated from it by a transverse partition, and has no connection with the cavity. Presently, between the oil bubble and the cavity arise a number of buds of various character (Fig. 108), which we will describe one by one, beginning with those nearest the oil bubble, since these upper members of the little swimming community bear a very im- portant part in its history. The infant community (Fig. 108) passes rapidly into the stage represented in Fig. 109, and then through all the stages intermediate between this and the adult, shown in its natural size in Fig. 115. The upper buds en- Fig. 107. Young Nanomia ; magnified. Fig. 108. Young Nanomia with rudimentary Please note that these images are extracted fr
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