The Early Development of the Pigeon's Egg. 29 



same egg, but I have not found such a mass of them in any other 

 egg. The nuclei are in the perivitelline fluid and at the place shown 

 in Fig. 12a they have collected in the furrows of accessory cleav- 

 age, and one of them (2) has followed a furrow to its deepest 

 limit. In this furrow some of the nuclei seem to be in a syncytium 

 without definite cell boundaries, while others are in entire and 

 separate cells. One such cell is enclosed between two delicate 

 layers of egg albumen (Fig. 12a, 1). Its nucleus has divided — per- 

 haps amitotically. 



There are two suggestions for the origin of these peculiar cells. 

 They may be : 



1. inwandering follicular cells, or 



2. supernumerary spermatozoa. 





=_py 



Fig. 13. — From a longitudinal section of a pigeon's egg, eleven and three- 

 fourths hours after fertilization, 7.15 a. m. vm., vitelline membrane, pv., 

 perivitelline fluid, s, one of the supernumerary spermatozoa, y, yolk. Leitz 

 4 / j\ Tube length 140 mm. 



If they are follicular cells, we should expect to find them occurring 

 quite constantly in all of the eggs of the pigeon. These structures 

 occur in 331/3 per cent of the eggs that I have studied, from four 

 to fifteen hours after fertilization. They occur in only 25 per cent 

 of my pigeon eggs from fifteen to thirty-nine hours after fertiliza- 

 tion, and not at all in later stages. Degeneration is their fate. In 

 the stages later than fifteen hours from fertilization, these cells were 

 very, scarce, — perhaps only 'one or two in an egg (Fig. 13). If the 

 follicular cells wander into the egg, there must be some quite regu- 

 larly occurring cause for their leaving the follicular epithelium. We 

 would not expect them to leave a compact epithelium amless they 

 are by nature wandering cells. Von Brunn ('82) describes the 

 entrance of follicular cells into ovarian eggs that are in the process 

 of resorption, but' says in a footnote, p. G, "Ueberhaupt ist ja wohl 



