2 DE. J. r. GEMMILL ON THE DEVELOPMENT OF 



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V. Gbneral Histobt and ExTBKNAi Chaeactbes dfking and apibk Metamorphosis 17 



Mode and site of attachment by the larval sucker, 17 ; fate of preoral lobe, and fonnation 

 of oral and aboral surfaces, 19; the hydrocoele pouches and order of their development, 

 20 ; numbering of pouches, 21 ; the aboral arm rudiments and their adjustment to the 

 pouches, 22 ; attachment by first-formed sucker-feet, 22 ; appearance of the eyes, the 

 mouth, the anus, and the spines, 23 ; constant position of anus in specimens with 

 normal and abnormal numbers of rays, and in S. papposa, 23 ; movements &c. of the 

 Starfish before and after formation of mouth, 24 ; surface-crawling, 24 ; chronology, 

 25. 



VI. Dbvblopmeni of Cavities and Oe&ans 25 



Formation of (1) anterior and (2) posterior ccelom, and of (3) middle chamber or euteron, 

 25. 



(1) Anterior Ccelom and its Derivatives 26 



Formation of right and left lateral diverticula, 26 ; hydroporic canal, 26 ; preoral 

 coelom, 26 ; epiderm of preoral lobe partly incorporated with oral surface 

 of Starfish, 27 ; separation of the right lateral diverticulum from axial coelom, 

 27 ; the hydrocoele groove, 28 ; formation of first five radial pouches, 28 ; forma- 

 tion of succeeding radial pouches, 28 ; relation of stalk of preoral coelom to 

 hydrocoele ring, 29 ; relation of pouch I to posterior coelom, 29 : the dorsal sac, 

 29 ; axial part of anterior coelom, 29 ; internal oral circular sinus, 30 ; axial 

 organ, 30 ; stone-canal, 31 ; relation of madreporic pores to stone-canal and axial 

 sinus, 31 ; pouch IX/I of external oral circular sinus, 31. 



(2) Posterior Ccelom and its Derivatives 32 



Dorsal and ventral horns, 32; extension of the horns, and the part played by them 

 in separating preoral coelom from axial and epigastric ooeloms, 32 ; septum in 

 madreporic interradius enclosing axial complex, 32 ; interbrachial septa, 33 ; 

 extension of hypogastric coelom on oral and aboral surfaces of enteron, 33 ; cir- 

 cular epigastric mesentery, 33 ; aboral ligaments of stomach and paired caeca, 

 34 ; formation and extension of pharyngeal coelom, 34 ; the circular hypogastric 

 mesentery, 35; hypogastric ligaments of stomach, 35; formation and subsequent 

 growth of pouches of external oral circular sinus, 35 ; genital rachis, &c., 36. 



(3) The Enteron 36 



Eadial lobes of stomach, 38 ; mouth, 39 ; anus, 39 ; paired radial caeca, 40 ; rectal 

 cseca, 40. 



VII. Development of the Skeleton 41 



Sequence in appearance of ambulacral and adambulacral plates, 41 ; plates of central and 

 marginal parts of disc, 41 ; terminals double, 42 ; transition to adult reticulum, 42 ; 

 development and grouping of spines, 43 ; the denticles, 43. 



VIII. HlBTOLOGI 43 



Mesenchyme and YolJc, 43 ; intracellular digestion of yolk, 44 ; reserve store retained in 



the mesenchyme, &c., 44 ; a more highly-yolked Starfish egg, 44 ; the hypenchyme, 45 ; 



yolk-granules in the enteron wall, 45. 

 A Statolith-liJce Body in the posterior coelom, 46 ; statocysts in Synapta, 46. 

 Nervous System, of larva, 46 ; relation to that of adult, 47 ; larval nervous system in other 



Echinoderms, 47. 



