1884.] 77 [Hyatt. 



the size of those in other specimens of the same species collected 

 at the same date, and the great irregularity of the cells makes it 

 probable that they were either diseased, or unimpregnated. 

 They are similar to the probably abnormal specimens described 

 by Dr. Sollas and referred to above. We have also seen more 

 advanced stages presenting similar pathological irregularities in 

 Chal. limbata and Hal. distorta. 



An amphiblastula of Tethya hispida was observed in which the 

 dome-shaped mass of endoblast cells formed one pole and the 

 remaining four-fifths to five-sixths of the oval body was occupied 

 by the still unciliated cells of the ectoblast. This specimen was 

 carefully studied and figured while living, and no blastulapore 

 was present. The cells of the endoblastic cap were slightly larger 

 than those of the ectoblast, but all distinctly hexagonal. The 

 cap at first sight reminds one of the outer layer of the endoblast 

 cells as figured by Keller in Chalinulafertilis (Zeitschr. Wis. Zool. 

 vol. xxxiii, pi. 18, f. 14) and were marked off by an exceedingly 

 distinct but shallow and narrow constriction. That it was hol- 

 low, seems to be assured by the examination of two other em- 

 bryos of the same species collected in the same dredging. These 

 had been treated with picric acid and were precisely similar in 

 every way but slightly smaller, and each showed a blastulapore 

 in the centre of the endoblastic cells. In one, the cells of the 

 rim were seven in number and larger than the surrounding cells, 

 while in the other no difference was apparent. This opening is 

 similar to that of Halichondria described above, and to that fig- 

 ured by Oscar Schmidt in Sycandra raphanus in a later stage after 

 the larva was more fully matured, the endoblast being ciliated. 

 (Zeitschr. Wissen. Zool. vol. 25, supp. 1875, pi. 9, f. 4-5.) The 

 opening does not seem to have been due to reagents, or to have 

 been closed by contraction in the living specimen, we think it 

 the exceptional retention of a younger characteristic in the 

 later stages of the embryos in which it occurs. Contraction 

 would be more likely to close an orifice than to make one. 



We have also observed several embryos very similar to the am- 

 phimorulae of Tethya, but presenting older characteristics, being 

 solid and in one example with an endodermal ciliated hemisphere. 

 This is very finely indicated in Keller's remarkable figure of the 

 larva of Esperia Lorenzii, pi. 20, f. 26, p. 341. In this larva with 



