August 18, 1905.] 



SCIENCE. 



211 



In Gnetum Gnenion, a gymnosperm (Fig. 

 2, D), cellular tissue is formed only at one 

 end of the female gametophyte, the end near- 

 est the micropyle remaining in the free nu- 

 clear condition. Any one of these free nuclei 

 may become an egg nucleus. 



In other species of Gnetum (Fig. 2, E) no 

 part of the female gametophyte gets beyond 

 the free nuclear condition. The number of 

 nuclei is likely to be smaller than in Gnetum 

 Gnemon. 



Peperomia, an angiosperm (Fig. 2, F), 

 shows a still more reduced condition, the ma- 

 ture female gametophyte containing only six- 

 teen free nuclei. A somewhat similar condi- 

 tion is found in Gunnera, where the number 

 of free nuclei varies from sixteen down to 

 eight. 



Most angiosperms (Fig. 2, G) have eight 

 nuclei in the female gametophyte, one of 

 these nuclei functioning as an egg nucleus. 

 This is the most reduced condition yet de- 

 scribed for an angiosperm. We have found, 

 quite recently, in Cypripedium, a mature fe- 

 male gametophyte containing only four nuclei. 

 The antipodal polar nucleus had not divided 

 and was disintegrating. One mitosis in the 

 micropylar end had also failed to take place. 

 One might reasonably hope to find still greater 

 reduction in the tropical orchids, so that while 

 the stage shown in Fig. 2, I, is still hypo- 

 thetical, it is not at all impossible that it may 

 exist. The megaspore would then function 

 directly as an egg and the four spores would 

 correspond strictly with the egg and the three 

 polar bodies. 



The series, as a whole, shows a gradual re- 

 duction of the gametophyte from an independ- 

 ent plant to a parasite; then a reduction 

 from a cellular condition to the free nuclear 

 condition; and finally a reduction in the num- 

 ber of free nuclei, until (admitting the hypo- 

 thetical case shown in Fig. 2, 7) the condition 

 shown by the animal egg with its three polar 

 bodies is reached. The behavior of the chro- 

 mosomes during the formation of the four 

 megaspores is essentially identical with their 

 behavior during the formation of the egg and 

 its polar bodies. 



It was only by the investigation of forms 



below the angiosperms -that the true nature of 

 the female gametophyte of angiosperms be- 

 came known. Perhaps a more thorough ex- 

 amination of animals below the Metazoa may 

 aid in interpreting the egg and its polar 

 bodies. 



Since there would be much repetition in a 

 discussion of the male gametophyte, this sub- 

 ject is omitted. 



I regret that Professor Beard's work was 

 overlooked. In this one particular Professor 

 Lyon's criticism must be accepted. The fact, 

 however, that Professor Beard relies strongly 

 upon apogamy to support his theory will indi- 

 cate to botanists a view-point somewhat dif- 

 ferent from mine. 



It is gratifying to note that Dr. Lotsy's ^ 

 recent paper on the x and 2a; generations is 

 directly in line with my theory. 



Charles J. Chamberlain. 



PRELIMINARY NOTE ON A GIGANTIC MAMMAL FROM 

 THE LOUP FORK BEDS OF NEBRASKA. 



During the summer of 1904 the writer was 

 fortunate in locating an important fossil 

 quarry in the upper series of the Loup Fork 

 formation on the Niobrara River, four miles 

 east of Agate P. O., Sioux County, Nebr., 

 upon the property of Mr. James H. Cook, the 

 Agate Springs Stock Farm. The existence 

 of fossil bones in this locality was known to 

 Mr. Cook as long ago as the year 1890, but he 

 regarded the fragments of bones, when he first 

 found them, as merely proving that the spot 

 had been occupied by the Indians as si burying 

 ground, they having freqviented the locality 

 in early days and frequently camped there. In 

 August, 1904, I was guided to the spot by Mr. 

 Cook's son, Harold J. Cook, and made some 

 preliminary investigation. The work has been 

 continued throughout the spring and summer 

 of the current year under my direction. An 

 interesting feature of the deposit is the great 

 number of water-worn fragments of bone 

 found in the quarry, clearly indicating that 

 the remains were subjected to the action of a 



^ Lotsy, J. P., ' Die ay-Generation und die 2a;-Gen- 

 eration, eine Arbeitshypotliese,' Biol. CentralMatt, 

 25: 97-117, four text diagrams, 1905. 



