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The following Memoir rdntos to a group of animnls of a somewhat octagonal 

 bowl-shaped form (not unlike that of a reversed umbrella), with tentacles clustered 

 in groups at each of the angles. These animals, formerly regarded as a group of 

 the Polyps, related to the sea-anemones, have in more recent times been associated 

 with the Acalephs or sea-nettles and jelly-fishes, and either combined with one of 

 the more comprehensive orders, or estimated as representatives of a peculiar and 

 independent order. This group, which was the subject of Professor Clark's 

 last studies, is in his judgment entitled to ordinal rank in tlie class of Acalephse. 

 The first part of the work is occupied with the " general and comparative mor- 

 phology" of the Lucernariae; and the second part is restricted to the "anatomy 

 and physiology of llalidystus auricula." In the first part are three chapters ; the 

 first on " individuality," in which are considered the questions relating to "polarity 

 and polycephalism," and " the hydroid and medusoid cephalisms." In the second, 

 the thesis that " the type of form is not radiate" is defended, and the form is 

 described as " the dorso-ventrally repetitive type." The third chapter is devoted 

 to the consideration of " antero-posterior (cephalo-caudal) repetition," and under 

 the heads of " the scyphostoma and ephyra varieties of the same morph" and " the 

 individuality of Pclagia and Lucernariae." 



In the second part are four chapters, the third to seventh of the entire work. 

 In the first (third of tlie work) are described the "general form and structure," 

 including habitat, habits, form, and size, the proboscis, the umbella, and the 

 peduncle In the second is considered the " organography, including the walls," 

 "the muscular system," "the tentacles, the marginal adhesive bodies, or colletocys- 

 tophorae," "the caudal adherent disk," "the digitiform bodies, or digituli," "the 

 digestive system," '' the nervous system," and " the reproductive system." 



In a third, are embraced the results of studies of the " embryology," or various 

 stages of growth of the species, including observations on " the egg and the sper- 

 matozoa ;" on " a young Haliclj/sius auricula, uenrly one sixteenth of an inch in 

 diameter ;" on " a specimen three thirty-seconds of an inch across the umbella;" on 

 " a young specimen one-eighth of an inch across ;" on the " special development 



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