96 SUMMARY OF CURRENT RESEARCHES RELATING TO 



an outer ectoderm is, indeed, recognizable, but this originates, not by the 

 modification of the everted ectoderm, but as a growth from the tentacles and 



basal pore. /, x mi 



His further experiments led him to these three conclusions: — (1) Ihat 

 the nature of tissues is constant, ectoderm is always ectoderm, and cannot 

 become endoderm ; (2) that for reconstruction of the whole from a part, 

 that part must contain representative portions of all three layers ; (3) that 

 the artificial division of Protozoa and Polypes lends support to the theory 

 of heredity suggested by Jager, clearly enunciated by Nussbaum, and 

 recently developed by Weismann — the theory of the continuity of the 

 germinal protoplasm. 



Structure and Development of Siphonophora.* — Prof. C. Chun finds 

 that the most common Siphonophore of the Mediterranean has never been 

 properly recognized; he gives it the name of Diplnjes suhtilis; its Eudoxia- 

 stacre was known to W ill, who applied to it the name of Erssea elongata. 

 The author gives a table showing the relation of the Eudoxia-atige to five 

 Mediterranean Calycophorids :— 



1. Cuhoides vitrem (?) Quoy and Gaimard) ^^^^ ^^entagona Eschscholtz. 

 Eudoxia cubotdes Leuckart ) •' ^ '' 



2. Eudoxia messanensis Gegenbaur .. .. ) ^. , ^^^^i^^ta Leuckart. 

 E. campanula LenckaTi ) ^ ^ 



3. Erseea truncaia Will .. ) Monophyes gracilis Clius. 



Diplopnysa tnernns {jtegenba.}xr .. .. } ens 



4. Erseea pyramidalis Will > Muggisea Kochii Chun. 



Eudoxia eschscfwltzit Bnsch ) •'^ 



5. Erseea elongata yf HI Diphyes suhtilis Chun. 



The author doubts the production of Eudoxia-stsigeB in any other of the 

 well-known Diphyids of the Mediterranean. 



Structure of Eleutheria.t — Dr. C. Hartlaub has a preliminary notice 

 on this small creeping Cladonemid ; it has a bell-cavity of the normal 

 width, which is bounded below by a broad velum. Below the zone of 

 tentacles the side wall of the cavity is formed by a well-developed urticating 

 ridge. The brood-cavity is placed on the dorsal side of the animal, and is 

 not the homologue of the canal of the manubrium of the medusa bud, for 

 it has no communication with the gastric cavity ; it is invested by a special 

 epithelium, and is connected with the bell-cavity b}' six interradial canals. 

 It is hermaphrodite, and its sexual cells are developed from the epithelium 

 of the brood-cavity, the female cells ventrally, and the male dorsally. 



The bell, in the ordinary sense of the word, is rudimentary, the radial 

 canals being extraordinarily short, and the peripheral part very delicate. 

 The urticating ridge reminds us of the same parts in the Trachynemidse and 

 Geryonidse, but is distinguished by the fact that it consists of an inner 

 layer which carries the stinging cells, and an investing epithelium, which, 

 to guess from the figures given by the Hertwigs, is wanting in the first- 

 mentioned forms. The velum, the presence of which has been hitherto 

 denied, is very broad, and may almost completely close the bell-cavity ; the 

 bell-wall does not serve as a propelling organ, but for a support and brood 

 pouch. 



The author was able to convince himself of the hermaphrodite nature 

 of this remarkable medusoid by means of a series of sections made on 

 fortunately selected examples; only twelve per cent, were found to be 



• SB. Prcuss. Akad. Wise., 1886, pp. C81-8. t Zool. Auzeig., ix. (1886) pp. 707-11. 



