On the Structure o/t/i€ Stylasteridae. 189 



The f^onophores are sometimes single in the ampullae, sometimes 

 in groups of two or three arising from u common base with 

 their contents in various stages of development. Tlie ripe sper- 

 matoAoa are precisely similar in form to those of Garveia nu- 

 tans*. In AUoporn, Acanthopora, and St ijliiater eruhescens the male 

 gonophores have a similar structure. \n tlie Stt/laster allied to 

 Cr>ipti>hAia the male elements are developed in a series of sacs, 

 which encircle the calide, often in a double row. The sacs spring 

 from the co?uosarca] network; they ct)ntain numerous smaller glo- 

 bular cysts, attached to a common basal endodermal tissue. These 

 cysts are some of them tilled with ripe sj)ermato7,oa, others with 

 spermatic cells in various stages. The female gonophores are, 

 in I'JrriiKi, simple, i. e. each ampulla contains only a simple ovum 

 or embryo, in Cn/ptohelia large sacs are present at the sides of 

 the calicles, which contain ova and embryos in all stages of develop- 

 ment. Only a single sac of the kind is developed in relation with 

 each calicle. In both genera the spadix in its earliest stage is cup- 

 shaped, the cup having fitted into it an ovum ^\-ith germinal vesicle 

 and spot well marked. The o\ a early lose the germinal vesicle 

 and spot, and develop into very large planulae, in the same manner 

 as, e. g., those in Laomedea fle.vuosaf. In Erriaa the planulte are 

 more ovoid in form than in Cryptohelia, in which they are long 

 and worm-like, measuring ^ of an inch in length. They have a thick 

 transparent ectoderm, abundantly supplied \\\i\\ the larger form 

 of thread-cells. The spadix in both genera, as the development of 

 the ovum proceeds, becomes divided at its margin into a series of 

 lobes, which lobes subdivide and encroach over the surface of the 

 ovum until more than half the proximal surface of the ovum is 

 thus embraced by the cup of the spadix. The lobes of the margin 

 of the spadix appear just like developing tentacles ; and the spadix 

 of Cryptohelia was at first supposed to be a developing actinula. 

 The out^r, thin, perforated calcareous walls of the ampullae in 

 Errina appear to get thinner as de\elopmeut of the embryo ad- 

 vances, until they fall away or are absorbed altogether, and give 

 free exit to the planula. In Cryptohelia the planulae probably 

 escape through the mouths of the calicles. The endoderm, spa- 

 dices, &c. are coloured red by a colouring-matter, soluble in spirit, 

 insoluble in glycerine, in Fulypora, Cryptohelia, and Errina. In 

 the Stylaster resembling Cryptohelia the coloration is dusky green. 

 The green colouring- matter is soluble in spirit, and yields an ab- 

 sorption-band in the spectrum. In Polypora the living layer of 

 coenosarc set free by decalcification is very thick, not merely a 

 thin superficial film as in Millepora ; indeed all but the most cen- 

 tral axial regions of the branches of the corals are in active life: 

 In the other genera the w^hole of the coral appears to maintain 

 its vitality, there being no dead region represented by a cavity 

 after decalcification. 



• ' A Monograph of the Gymnoblaatic or Tubularian Hyclroicis,' by G. J. 

 Allman, M.D. &c., Ray Soc. part 1. pi. xii. fig. 9. 

 t Allman, /. c. p. 86. 



