14 XV. Echinodermata (mit Einschluss der fossilen) für 1903. 



portant. The temperature of the sea-water to which the eggs are 

 returned for development is probably less vital, although the rate is 

 slower at low temperatures. 



Mac Bride, E. W. (I). The Development of Echinus esculentus, 

 together with some points in the Development of E. miliaris and 

 E. acutus. In: Philos. Trans. R. Soc. London, Vol. 195B. p. 285—327. 

 Taf. 7—16. 



Autorreferat. „1. The blastula of Echinus contains a comparatively 

 thick Solution of proteid, which becomes thinner as development 

 advances, but some of which is found in the blastocoel throughout 

 the whole course of development, and eventually forms the jellylike 

 ground-substance of the test of the adult. 2. The Mesenchyme cells 

 are connected with each other and the wall of the blastula by proto- 

 plasmatic strings, but besides these no other protoplasmic structures 

 were observed in the blastocoel of the living blastula. 3. The adoral 

 ciliated band is formed from both ectodermic and entodermic cells 

 and produces an inwardly directed current and hence cannot be coni- 

 pared to the endostyle of the Protovertebrata. 4. The madreporic 

 pore is at first a structure distinctly belonging to the left side. 5. The 

 coelum undergoes a metameric segmentation into three divisions on 

 each side of the larva, but the segmentation of the left side precedes 

 that of the right. 6. The left functional hydrocoel has at first the 

 form of a disc, which is very early converted into a ring, through 

 which the adult Oesophagus later grows. 7. There is a well-developed 

 nervous System in the shape of an apical plate of neuro-epithelium, 

 corresponding in position to the apical plate of the Tornaria larva, 

 but this plate is not recognisable tili the larva is 3 weeks old. 8. The 

 epineural canals of the adult are derived from invaginations of the 

 ectoderm. 9. The lantern-coelom of the adult is homologous with the 

 outer perihaemal ring of the asterid and like it is derived from five 

 evaginated pockets of the coelom of the left side; the teeth and jaws 

 are developed from the walls of these pockets. 10. The blood-system 

 of the adult originates from the envelope of jelly investing the gut. 

 This jelly becomes changed by the infiltration of some substance 

 exsuded from the gut cells. 1 1 .The genital stolon aiises, as in Asteroidea, 

 as an outgrowth of the wall of the left posterior coelom, and the genital 

 rachis and the genital organs are developed from it. 12. The aboral 

 sinus, as in Asteroidea, is developed as an extension of the left posterior 

 coelom. 13. The first coil of the alimentary canal of the sea-urchin 

 is directly derived from the flexure of the larval gut ; whilst the second 

 or recurrent coil is slowly developed after the formation of the adult 

 arms by the lengthening of the intestine. 14. The sea-urchin immediately 

 after its metamorphosis exhibits many resemblances to an asterid 

 and this leads to the belief that the Echinoidea are derived from the 

 Asteroidea. 15. The general conclusions as to the ancestry of the 

 phylum Echinodermata as a whole, drawn from the study of the 

 development of Asterina gibbosa, are confirmed by the development 

 of Echinus esculentus, but the development of the echinopluteus as 



