468 Frogs of the Okefiiiokee Swamp 



to rotate the egg through cUiary action, previous to the closure of the medul- 

 lary folds. That cilia are entirely absent on the eggs of Engysloma is proved 

 by the fact that at the time the medullary groove is still open every egg of 

 the same age is in exactly the same position in respect to the center of the 

 earth, and remains so for a long time, or until the tail fold is well developed 

 and the medullary groove has been closed. Before the closure of the medul- 

 lary groove, but after the egg has begun to elongate and the paired, secretory, 

 adhesive surfaces of the under side of the head have appeared as rudiments, 

 the position of the animal and vegetative poles is still the same as in the 

 undeveloped ovum. The head end of the egg is slightly elevated above the 

 caudal end. This is due to the forward growth of the head, and the retention 

 of the heavier yolk, farther backward under the posterior half of the medul • 

 lary groove. The medullary groove thus, comes to be inclined downward 

 a few degrees from the head toward the tail, but the groove looks exactly 

 toward the zenith, while the yolk looks downward in every egg, even the 

 inclination of the medullary groove with respect to the horizon being the 

 same for every egg of the same age. 



"At this stage I neglected to note an extremely important fact,— Viz., 

 whether the cephalic and caudal poles of the same row of eggs were all of 

 them lying in the same direction. The fact that no change of position occurs 

 for a long time in the eggs of Engysloma would indicate that possibly we 

 might find that the future cephalic pole of the egg bore a constant relation 

 to the cephalic pole of the parent Engysloma, such as is known to be the 

 case in Balrachus lau. Such relations between parent and offspring exist to 

 a marked degree, if they are not universal, in plants, and it is desirable to 

 know to what extent the same rule holds with respect to animals. According 

 to what has preceded, the early development of Engysloma is peculiarly 

 favorable for the purpose of testing the theory that the cephalic and caudal 

 polarities of the parent are transmitted directly to the offspring, or that the 

 future long axis of the embryo already conforms, even in the egg, to that 

 of the parent. 



"The next step in the development of Engysloma is somewhat similar to 

 that of Rana. As soon as the larvae have the tail-fold well developed they 

 turn over and lie on the side, curved upon themselves, within the egg-evelope. 

 This is the condition of the eggs on the second and early part of the third 

 day. On the third day the larvae leave the egg, and then tend to fall upon 

 the bottom of the pool or receptacle in which hatching occurs. Soon after 

 this they begin to swim about actively, and, singularly enough, instead of 

 swimming like a fish, for some reason, which it is difficult to make out, the 

 larvae revolve on their own axes. This singular mode of locomotion is 

 probably due to the peculiar manner in which the tail is vibrated. This 

 mode of swimming lasts about a day, after which the larvae begin to swim 

 in the usual fish-like way. At this stage, when the larvae come to the surface, 

 the head is in contact with the surface of the water, and when quiescent the 

 axes of the body, when in a condition of equilibrium, assumes an angle of 

 about eighty degrees with the surface. The adhesive organs near the mouth 



