58 SUMMABY OF CURBENT BESEABCHES BELATING TO 



both are formed from two distinctly separated cell-layers ; in tlie 

 outer there appear chitinous hooks or setigerous plates or a large 

 number of cilia. The chitinogenous layer and the investing membrane 

 are formed in very much the same way. 



Striking as the resemblances are, it is not impossible that it is 

 merely accidental, and that the outer cell-layer of the Taenioid 

 embryo is not comparable to the ectoderm of the young Trematode, 

 but only to the underlying layer of epithelial cells. Further investi- 

 gations on taeniae are necessary to the resolution of this problem ; 

 if it should be shown that they do lose their ectoderm we should 

 have, in these two groups, the only known examples of the complete 

 loss of a germinal layer, inasmuch as Kleinenberg's observations 

 on a similar phenomenon in Hydra appear to stand in want of 

 revision. 



Simondsia paradoxa-* — This remarkable parasite was briefly de- 

 scribed by Dr. Cobbold in his ' Entozoa,' from some specimens dis- 

 covered by Professor Simonds in the stomach of a German hog that 

 had died in the Zoological Society's Gardens. The drawings and speci- 

 mens were temporarily lost, but, having been fortunately recovered, 

 Dr. Cobbold has been enabled to add considerably to his former 

 description of the parasite. The most striking feature in the 

 organization of the worm is a large rosette-shaped organ which 

 represents a prolapsed uterus entirely comparable to the prolapsed 

 uterus of Sphcerularia hombi. The male, which is slightly smaller 

 than the female, presents no specially interesting points of struc- 

 ture. In the female all the ovarian tubules and the uterine branches 

 are contained within the rosette, but the position of the external 

 opening could not be made out with certainty, though it is 

 apparently situated at the base of the rosette in the ventral line. 

 Each female is inclosed in a single cyst, the head alone projecting ; 

 the interior of the cyst shows a perfect cast of the rosette-shaped 

 organ ; the males are free. 



Monograph of the Melicertidse.t — L. Joliet finds that of all 

 rotifers the Melicertidse are those which are best adapted for the 

 investigation of the processes of development, inasmuch as after the 

 eggs are laid they are protected by the tube, and eggs are laid every 

 day, and development is completed in three days. 



To the three species, M. ringens, M. pilula Collins, and M. tyro 

 Hudson, the author adds a fourth, M. pedunculata, which most 

 nearly resembles the first, but is distinguished from it by being not 

 free in its tube, but attached to it by a seta which is fixed to the 

 end of its tail; the new species would seem to be rare, having as 

 yet been found only at Nogent-la-Phaye, near Chartres. The pond 

 in which it was found was for several years preceding the last two 

 completely dried up ; the so-called winter eggs are not formed in the 

 winter only, but throughout the season of activity. 



After a description of the general farm, Joliet deals with the 



* Trans. Linn. Soc— Zool,, ii. (1883) pp. 357-61 (1 pi.)- 

 t Arch. Zool. Exper. et Gen., i. (1883) pp. 131-224 (3 pis.). 



