79 



meget stærk Forstørrelse synlige Anlæg til temme- 

 lig store, med et opakt Inclliold fyldte Kapsler. I 

 enhver FoUikel findes altid 4 Celler eombinerede. 

 I de mindste Follikler (Fig. 13) er blot Ivjernerne 

 synlige, medens i de storre Follikler (Fig. 14, 15), 

 de enkelte Celler skarpt afgrændser sig fra hver- 

 andre. Af de 4 Celler er det alene den yderste, der 

 repræsenterer den egentlige Æg-celle; de 3 ovrige 

 er kun bestemte til dennes Ernæring og absorberes 

 derfor tilsidst ganske. Denne polare Celle skiller 

 sig ogsaa kjendeligt fra de 3 øvrige derved, at 

 Kjernen er mindre skarpt contnreret. Paa den fuldt 

 ndviklede Ægcelle vinddrager sig tilsidst Kjernen 

 ganske for Observation en, og heller ikke Kjernerne 

 i de 3 Næringsceller kan sees paa Grund af den 

 opake, gulbrune Næringsblomme, som nu fylder det 

 hele Æg (se Fig. 12). Er Æggene modne, træder 

 de ind i Ovariernes indre Hule og udtommes derfra 

 successivt gjennem Æglederen i Ilte Fodpars Æg- 

 kapsel, hvor de omgives med en temmelig fast Skal 

 (Fig. 16). Denne sidste viser sig ved stærk For- 

 storrelse' (Fig. 16 ') meget fint reticuleret, og dannes 

 rimeligvis ved et af Kapselens Vægge afsondret 

 Secret. 1 hver Ægkapsel finder man i Regelen kun 

 et meget begrændset Antal Æg, fra 1 enkelt (se 

 Tab. XII, Fig. 17, ov) til 4, og de forbliver her kun 

 en ganske kort Tid, idet de successivt udtømmes af 

 Kapselen og falder tilbunds, hvor de indleires i 

 Mudret, for til næste Sommer at udvikle sig til en 

 ny Generation. 



Testes har samme Beliggenhed som Ovarierne 

 og ligner ogsaa ved første Øiekast disse i Udseende. 

 Ved nærmere Undersogelse viser imidlertid Follik- 

 lerne sig forholdsvis mindre og af mere uregelmæs- 

 sig, noget affladet Form og ligesom slyngede ind i 

 hinanden (se Tab. XIII, Fig. 17). I enhver Follikel 

 er der (se Fig. 18) en indre Hule, der staar i For- 

 bindelse med det centrals Hulrum, og fra FoUikler- 

 nes Vægge udvikler Sædelementerne sig i Fonn af 

 meget smaa simple Celler (Fig. 19). Hvor Testes 

 udmunder, har det ikke lykkets mig at faa con- 

 stateret. 



ITdvikling. 



Jeg har heller ikke af denne Phyllopode kun- 

 net forfølge den hele Udvikling, men har dog leilig- 

 hedsvis faaet fat paa en Del Larvestadier, som jeg 

 her noget noiere skal omtale. 



Det tidligste observerede Stadium er afliildet 

 Tab. XI, Fig. 4, og Detailler af samme, Tab. XIII, 

 Fig. 21—27. 



Legemet har en Længde (fraregnet Haletraa- 

 dene) af kun omtrent 2 mm., og er halvt gjennem- 

 sigtigt, af gulrød Farve. 



ments, only visible under a very high power of the 

 microscope, to rather large capsixles with opaque 

 contents. In each follicle, 4 cells are always found 

 combined. In the smaller follicles (fig. 13) only the 

 nuclei are visible, while in the larger ones (figs. 14, 

 15) the cells are sharply divided from one another. 

 Only the outermost of the 4 cells represents the 

 egg-cell proper; the other 3 onl}^ serve to nourish 

 that one, and are therefore at last completely ab- 

 sorbed. This polar cell is also easily distinguishable 

 from the other three by the less distinctly ovitlined 

 nucleus. In the fully developed egg-cell, the nucleus 

 at last entirely withdraws from sight, nor can the 

 3 alimentary cells be seen on account of the opaque, 

 yellowish-brown food-yolk which now fills the entire 

 ovum (see fig. 12). When the eggs are mature, they 

 enter the inner cavities of the ovaries, and are 

 thence evacuated successively through the oviduct 

 into the egg-capsivle of the 11th pair of legs, where 

 they are enveloped in a rather firm shell (fig. 16). 

 This, when highly magnified (fig. 16), appears to be 

 very finely reticulated, and is probably formed by 

 a secretion from the walls of the capsule. In each 

 capsule there is found, as a rule, only a very limi- 

 ted number of ova, from a single one (see PI. XII, 

 fig. 17, ov) to 4, and they remain there only a very 

 short time, being discharged successively from the 

 capsule, when they fall to the bottom, and are im- 

 bedded in the mud, to develope in the following 

 summer into a new generation. 



The testes occupj^ a similar position to the 

 ovaries, and also, at first sight resemble them in 

 appearance. Upon closer examination, however, the 

 follicles prove to be relatively smaller, and of a 

 more irregular, somewhat flattened shape, and are, 

 as it were, twisted about one another (see PI XIII, 

 fig. 17). In every follicle (see fig. 18) there is an 

 inner cavity, in communication with the central ca- 

 vity, and the sperm elements develope from the 

 walls of the follicles in the form of very small 

 simple cells (fig. 19). I have not .succeeded in ascer- 

 taining- where the testes discharge themselves. 



Development. 



Of this Phyllopod too, I have been unable to 

 follow the whole course of development, bivt have 

 however occasionally succeeded in finding certain 

 larval stages, which I will here describe more 

 minutely. 



The earliest stage observed is figured on PI. XI, 

 fig. 4, and details of the same on PI. XEI, figs. 

 21—27. 



The body has a leng-tli (not including the caudal 

 filaments) of only about 2 mm. and is semi-trans- 

 parent and of a yellovi'ish-red colour. 



