(18) 



EXPLANATION OF THE PLATES. 



tlian i^; 6 the same as ?;, but still nearer to the eve; 

 ( where 7/ and d nier^^e into one outhiie ; h the eavity 

 between the outer and inner walls of r; /I hollow 

 of tlie tentaele ; ^ entrauee to /i ; o suiiericjr margin 

 of the soeket from whieh P arises. 2IHI diameters. 

 Fig. 4. The same as fig. 3, but seen from below, with the 

 following additional letters : v the same as /I, but fore- 

 shortened by the curvature of the tentacle ; i tlu' in- 

 ierior margiu of the socket from which the tentacle 

 arises; - the broad line of attachment of the veil (/). 

 :i(lO diameters. 

 Fig. .■>. lulerior side of a quarter of figs. .') aud I'o of PL 

 XI''., principally to show the branching of the radi- 

 ating canals, the extent of the veil, and tlie fringes 

 (") of the jirobiiscis. '2i diameters. 

 Fig. ti. The fringes (a) of the proboscis of fig. 5 in 



profile. 

 Fig. 7. Cells (<•) aud lasso-cells (n h) from the upper 



surface of the disk of fig. 0. .5iiO diameters. 

 Fig. s. The same as (/' fig. 2, more enlarged. » entrauee; 

 j3 <lorsal side toward the outer veil ; ) ]irolile of the 

 wall at the dorsal side of the bend; '1 [irofile of the 

 lower side of the curve. IdH diameters. 

 Fig. [I. View similar to (ig. 4, from the same cphyra as 

 fig. 2. The letters as iu fig. 4 excepting e, which 

 is the outer wall of a very young lobule developing be- 

 tween the larger ones ; p cavity of the young lobule 

 (f); f groups of lasso-cells. 100 diameters. 

 Fig. ]0. Cellular tissue I'rom the proboscis of an adult 



Aiirelia, treated with alcohol. 500 diameters. 

 Fig. 1 1 . The eye aud the inunediate organs, seen obliipicly 

 from the outer enil. Iu addition to the general letter- 

 ing, there is a the entrance to </' ; li the dorsal side 

 of the external ludf of </■ ; 5 profile of tlie wall at 

 the bend of (/' ; t ; the wall of -/'. I'oo diameters. 

 Fig. 12. The .same as fig. 10, but iu a natural state. 



."joii diameters. 

 Fig. i:i. .Similar to fig. :!, but from fig. lli. The figures 

 I 2 2.^ ;i refer to tin- tentacles, from the oldest to 

 the youngest. Lettering as iu fig. 2, with this difit-r- 

 encc, that ^ is seen through the tentacles ; 7 where 

 the outer wall of the tentacles passes into that of its 

 neighbor. 100 diameters. 

 Fig. 14. I'rofile sectional view of the walls of the hydra 

 stem of Coryne mirabilis. a the horn-like sheath ; h 

 cells of the outer wall; li' mesoblast of A; c the .same 

 as b, seen iu the distance ; </ cells of the inner wall ; 

 lid brown cells; e the same as (/, in the distance. 

 500 diameters. 

 Fig. 15. A lasso-cell from the outer wall of fi^T. 14. 



a the cell wall ; h the straight part of the thread ; 

 c d <- the first, second, and third coils ; _/' aperture of 

 the cell aud base of h. 2,000 diameters. 



PLATE XII. 



Pf.l.\gia cvanell.\, Per. aud LcS. 



[I'ruwn from n.itiire \<y .T. liiirtldiarilt.] 



Fig. 1. I'rofile view, natural size. 



Fig. 2. View from below, the mouth appendages being 



removed, a arms ; h ovaries ; c mouth ; d tentacles ; 



e ejes. 

 Fig. ?•. View from aliove. a cyci^'., h chymiferous tubes ; 



(■ digestive cavity; </ tentacles. 

 Figs. 4 to 10. rianuUi? and cphyra of the same. 

 Fig. 4. Young planula, seen in jirofile. 

 Fig. 5. Older planula, seen in profile. 

 Figs, t! and 7. Older planula, seen from above, and iu 



profile. 

 Figs, .s and 11. Passage of the jilainila into the ephyra, 



in profile fig. 8, aud from below tig. 0. 

 Figs. 10 aud 11. Young ephyra, in profile and from 



below. 

 Fig. 1 2. Older ephyra, from Ijelow. c mouth ; h eye- 

 specks; (I position of the tentacles at a more advanced 



period. 

 Fig. i;i. jNIaguified spberomere in connection with the 



mouth. (( chymiferous lobes ; // eye ; c mouth. 

 Figs. 14 aud 15. Magnified eyes. a eye proper; h 



ch}inifcrous tube of the eye. 

 Fig. IG. ]\Iagnified mouth, still simple and without arms. 



PLATES XIII. aud XII^. 



PoLYCLONLV FR()XI>i:iS.\, AiJ. 

 [Ilniwii from uaturo by ,1. liiirrkliardt.] 



Pi..\TE XIII. Profile view and various structural details 

 of rolyclonia frondosa. 



Fig. 1. Profile view of our Polyclonia (the ^Medusa fron- 

 dosa of Pallas), with the oral appendages drawn up 

 under the disk. 



Fig. 2. The same, seen from below, difterent parts being 

 removed in different segments and shown in a diifer- 

 cnt condition in each. eyes, twelve in number. 

 In. segments 1 antl 2 may be seen the two branches 

 of one arm with their marginal lobes entire, aud 



