388 SUMMARY OF CURRENT RESEARCHES RELATING TO 



pass out with the excrement of the bat and probably hatch in water, 

 whence the larvje may pass into the insect. In any case, the inter- 

 mediate host has been discovered. 



Some Swiss Cercarise.*— 0. Fuhrmann describes a new kind of 

 cercaria {Cercaria htifera sp. n.) with a forked tail which occurred in 

 Limnsea aurkularia. The cercariae are formed within sporocysts, and 

 when they are liberated they attack fishes with rapidly fatal results. 

 Through skin and gills they enter the circulation, and by means of 

 their anterior armature and ventral sucker cause haemorrhage. They 

 also block the capillaries. The final host is probably a fish or a fish- 

 eating bird. Fuhrmann also describes a new cercaria {Gercariaeum 

 squamosum sp. n.) which has no trace of tail. Redife were found in 

 Limnaea auricularia, var. ampla, and there were eighteen to thirty 

 cercari;B in each. There is a characteristic investment oi minute scales 

 covering the whole body, except a median line between the buccal and 

 the ventral sucker. 



Development of Emplectonema g-racile Stimpson.t— H. C. Pelsman 

 has studied the develupnient of this Nemertean. The eggs are laid 

 singly, each in a gelatinous envelope. The diameter is 135-140 jx. 

 The cleavage is of the spiral type, alternately to right and left. In 

 contrast to what occurs in Annelids, Molluscs, and Polyclads, there 

 is a strong development of the animal half. In the <s-cell stage the 

 four cells of the first ectomere quartet are considerably larger than the 

 four cells at the vegetative pole. The four quadrants are and remain 

 tilike. The larger cells divide more rapidly than the smaller (Kofoid's 

 law). The smaller cells of the vegetative half lag behind those of the 

 animal half. In consequence of this the difference in size between the 

 two halves disappears, and a division of the fourth quartet does not 

 take place before gastrulation, so that is cannot be determined whether 

 4,d, the mother-cell of the coelomic mesoblasts in the types mentioned 

 above, differs from 4a, 46, 4c. The radial symmetry is not disturbed 

 before gastrulation, as it is in the other cases. It was not possible to 

 observe the origin of the ectomesoderm. The gastrulation is at first 

 like that in those Annelids and Molluscs that have eggs with little yolk. 

 But the epithelial arrangement of the endoderm cells soon disappears. 

 They form an irregular mass with which immigrant cells from the 

 ectoderm are associated. Gastrocoel and blastocoel disappear. Flattened 

 ectoderm cells form a thin ciliated larval envelope ; the others sink in 

 and form a compact undifferentiated mass, suggesting the pupaj of flies. 

 Thus there is a well-marked metamorphosis. 



Coelentera. 



Structure and Development of Sporosacs of Dicoryne.J — J. H. 

 Ashworth and James Ritchie have studied colonies of Dkonjne comjbearel 



* Rev. Suisse Zool., xxiv. (1916) pp. 389-96 (1 pi.). 



t Tijdschr. Nederlaud. Dierk. Ver., xiv. (1915) pp. 68-114 (i pis. and 2 figs.). 



J Trans. Roy. Soc. Edinburgh, li. (1915) pp. 257-85 ( 3 pis. and 3 figs.).. 



