No. 2.] THE ECHINODERM SPERMATOZOON. 269 



Fig. 33. Spermatocyte : Stichopus regalis. After division of the nuclei to 

 form two spermatids. The cytomicrosomes which formed the spindle, previously 

 inside the nucleus, are now in the cytoplasm. 



Fig. 34. A Spermatid of Stichopus regalis. The cytomicrosomes are fusing 

 into larger masses, 7n, which will ultimately fuse and form the mitosome. The 

 centrosome is plainly in the cytoplasm. 



Fig. 35. A metamorphosing Spermatid of Stichopus regalis. Sea-water + 

 dahlia and methyl green preparation. Shows a later stage in the formation of the 

 mitosome, and of the tail. 



Fig. 36. A metamorphosing Spermatid of Stichopus regalis. Sea-water + 

 dahlia and methyl green preparation. Shows a later stage in the formation of the 

 mitosome, and of the tail. 



Fig. 37. Spermatogone: Asterias Forbsii. Flemming (24 hours); distilled 

 water (48 hours) ; Delafield's haematoxylin ; dilute glycerine. 



Fig. 38. Spermatocyte: Asterias Forbsii. Flemming (24 hours); distilled 

 water (48 hours) ; Delafield's haematoxylin ; dilute glycerine. 



Fig. 39. Spermatid : Ophyoglypha lacetosa. Sea-water -f- dahlia and methyl 

 green. 



Fig. 40. Metamorphosing Spermatid of Ophiothrix fragilis. Platinum 

 chloride 0.3% {12 hours): dahlia and methyl green. Shows mode of formation 

 of mitosome, and of the tail. 



Fig. 41. Spermatid of Chaetaster longipes. Platinum chloride 0.3% (12 hours); 

 dahlia and methyl green. Shows mode of formation of mitosome, and of the 

 tail. 



Fig. 42. Metamorphosing Spermatid : Chaetaster longipes. Platinum chloride 

 0.3% (12 hours); dahlia and methyl green. Shows mode of formation of mitosome, 

 and of the tail. 



Fig. 43. Metamorphosing Spermatid : Chaetaster longipes. Platinum chloride 

 0.3% (12 hours); dahlia and methyl green. Shows mode of formation of the 

 tail. 



Fig. 44. Metamorphosing Spermatid nearly transformed into the sperma- 

 tozoon. Sphaei-echimis granularis. Sea-water + dahlia and methyl green. 



Fig. 45. Metamorphosing Spermatid nearly transformed into the sperma- 

 tozoon. Arbacia pustulosa. Chloride of manganese 10% + dahlia and methyl 

 green. 



Fig. 46. Metamorphosing Spermatid : Echinus microtuberculatus. Sea-water 

 -f- dahlia and methyl green. 



Fig. 47. Metamorphosing Spermatid nearly transformed into the sperma- 

 tozoon. Arbacia pustulosa. Chloride of manganese 10% -f- dahlia and methyl 

 green. 



Fig. 48. Spermatid nearly transformed into a spermatozoon. Sphaerechinus 

 granularis. Sea-water -f dahlia and methyl green. 



Fig. 49. Spermatid, almost completely transformed Asterias glacialis. Osmic 

 vapor. Centrosome and mitosome seem to be rendered more refringent, and are 

 blackened somewhat more than the rest of the cell. The mitosome has not yet 

 become a single mass. 



Fig. 50. Spermatid nearly transformed into a spermatozoon. Arbacia pustu- 

 losa. Chloride of manganese 10% -\- dahlia and methyl green. 



