TABLE IV. 



Systematic Survey of the five earliest germinal stages of Animals with 

 refei'ence to the four different type-forms of Egg-cleavage. 



A. Total Cleavage. 



{Segmcntatio totalis.^ 



a. Original or primor- 

 dial cleavage. 



I- a. Archi- 

 monerula. 



(Fig. 22 A, p. 191.) 

 A cytod in which 

 the formative and 

 nutritive yelk are not 

 distiDct. 



n. a. Archi- 

 cytula. 

 (Plate II. Fig. 1.) 

 Parent-cell which 

 has arisen out of the 

 archi-monerula by the 

 formation of the pa- 

 rent-kernel. 



III. o. Archi- 

 morula. 



(Plate II. Fig. 3.) 

 A solid (generally 



globular) heap of 



similar cells. 



IV. a. Archi- 

 blastula. 



(Plate II. Fig. 4.) 

 A lioUow (usually 

 globular) vesicle, tlie 

 wall of which consists 

 of a single layer of 

 similar cells. 



V. a. Archi- 

 gastrula. 



Bi'll-gustrula. 

 (Platell. Fig. e.) 

 Fig. 2.3-2S, p. 193. 

 Primitive intestine 

 empty, without nu- 

 tritive yill<. Pri- 

 mary Kirni - layers 

 one-layered. 



b. Unequal cleavage. 



B. Partial Cleavage. 



(^Segmentatio partialis.) 



c. Discoidal cleavage, d. Superficial cleavage. 



I. b- Amphi- 

 monerula. 



A cytod which 

 includes formative 

 yelk at the animal 

 pole, nutritive yelk 

 at the vegetative 

 pole : the two are 

 not very distinct. 



II. &. Amphi- 

 cytula. 



(Plate II. Fig. 7, 12.) 

 Parent-cell which 

 has arisen out of the 

 amplii-monerula by 

 tlie formation of the 

 parent-kernel. 



III. b. Amphi- 

 morula. 



(Plate II. Fig. 9.) 

 A roundish heap 

 formed of two kinds 

 of cells, the animal 

 cells at one, the vege- 

 tative cells at the 

 other pole. 



IV. b. Amphi- 

 blastula. 



(Plate II. Fig. 10.) 

 A roundish vesicle, 

 the wall of which at 

 the animal pole con- 

 si.-t.s of smaller cells, 

 at the vegetative 

 pole of larger cells. 



V. b. Amphi- 

 gastrula. 



Ilooil-gastrula. 



(Plate II. Fig. 11,17.) 



Fig. 32-35, p. 206, 



Fig. 41. 



Primitive intestine 



partly tilled witli 



segmented nutritive 



yelk. Germ-layers 



often many -layered. 



I- c. Disco- 

 monerula. 

 A cytod which 

 includes formative 

 yelk at the animal 

 pole, nutritive yelk 

 at the vegetative 

 pole : the two are 

 quite distinct. 



II. c. Disco- 



cytula. 



(Plate III. Fig. 18.) 



Parent-cell which 



has arisen out of the 



disco-monerula by 



the formation of the 



parent-kernel. 



III. c. Disco- 

 morula. 

 (Plate III. Fig. 21.) 

 A flat disc, com- 

 posed of similar cells 

 on the animal pole 

 of nutritive yelk. 



IV. c. Disco- 

 blastula. 



(Plate III. Fig. 22.) 

 A roundish vesicle, 

 the small hemisphere 

 of which consists of 

 cleavage -cells, the 

 larger of nutritive 

 yelk. 



V. c. Disco- 

 gastrula. 



Disc-gastrula. 



(Plate III. Fig. 24.) 



Fig. 43. p. 219, 



Fig. 49, p. 22H. 



Primitive intestine 



filled with nnseg- 



niented nutritive 



yelk. Flat germ-disc. 



I. d. Peri- 

 monerula. 

 A cytod which in- 

 cludes formative yelk 

 in the outer wall, 

 nutritive yelk in the 

 centre. 



n. d. Peri- 



cytula. 



(Plate III. Fig. 25.) 



Parent-cell which 

 has arisen out of the 

 peri-monerula by the 

 formation of the pa- 

 rent-kernel. 



III. d. Peri- 

 morula. 



(Plate III. Fig. 27.) 



A closed vesicle : a 

 cellular stratum sur- 

 rounds the whole cen- 

 tral nutritive yelk. 



IV. d. Peri- 



blastula. 



(Plate III. Fig. 28.) 



A closed vesicle : a 

 cell layer surrounds 

 the whole nutriiive 

 yelk {— Peri-morula). 



V. d. Peri- 

 gastrula. 



Bladder-gastrula. 

 (Plate III. Fig. 29.) 



Cleavage-cavity fill- 

 ed with unsegmented 

 nutritive yelk. Pri- 

 mitive intestine dif- 

 lereut. 



