TABLE IV. 



Systematic Snrvcy of tlie five earliest germinal stages of Animals with 

 reference to the fonr different type-forms of Egg-cleavage. 



A. Total Cleavage. 



(^Segmentatio totalis.') 



A 



'■"'SS^ST'- ^ Coequal cleaTage. 



I. a. Archi- 

 monerula. 



(Fig. 22 A, p. 191.) 

 A cytod in which 

 the formative and 

 nutritive yelk are not 

 distinct. 



II. 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. a. Archi- 

 morula. 



(Plate II. Fig. 3.) 

 A solid (generally 



globular) heap of 



similar cells. 



IV". a. Archi- 



blastula. 

 (Plate II. Fig. 4.) 

 A hollow (usually | 

 globular) vesicle, the 

 wall of which consists 

 of a single layer of 

 similar cells. 



V. a. Archi- 

 gastrula. 



Bell-gastrula. 

 (Plate II. Fig. 6.) 

 Fig. 23-28, p. 193. 



Primitive intestine 

 empty, without nu- 

 tritive yolk. Pri- 

 mary Kcrm - layers 

 one-layered. 



I- &• Amphi- 

 monerula. 



A cj-tod which 

 includes fonnative 

 yelk at the animal 

 pole, nutritive yelk 

 at the vegetative 

 pole : the two are 

 not very distinct. 



II. b. Amphi- 



cytula. 



(Plate II. Fig. 7, 12.) 



Parent-cell which 

 has arisen out of the 

 araphi-monerula by 

 the formation of the 

 parent-kernel. 



III. &. 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>ts of smaller cells, 

 at the vegetative 

 pole of larger cells. 



V. b. Amphi- 

 gastrula. 



Hood-gastiula. 



(Plate II. Fig. 11,17.) 



Fig. 32-35, p. 206, 



Fig. 41. 



Primitive intestine 

 partly filled with 

 segmented nutritive 

 yelk. Gevm-layers 

 often many-layered. 



B. Partial Cleavage, 



{Segmentatio partialis.) 



c. Discoidal cleavage. 



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 



j 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. 228. 



Primitive intestine 

 filled with unseg- 

 mei)ted nutritive 

 yelk. Flat germ-disc. 



d. Superficial cleavage. 



I. d. Peri- 

 monerula. 

 A cytod which in- 

 cludes formative yelk 

 in the outer wall, 

 nutritive yelk in the 

 centre. 



II. 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 laj'er surrounds 

 the whole nutritive 

 yelk {= Peri-morula). 



V. d. Peri- 

 gastrula. 



Bladder-gas trula. 

 (Plate III. Fig. 29.) 



Cleavage-cavity fill- 

 ed with unsegmented 

 nutritive yelk. Pri- 

 mitive intestine dif- 

 ferent. 



