324 Morphologie, Teratologie, Befruchtung, Cytologie. 



spirems. Throughout this period the chromosomes have retained 

 their individuality. 



The spirem, which consists of 16 end to end chromosomes, will 

 take the form of radiating loops during second contraction, segmen- 

 tation occurring at the outer bend. Each of the bivalents so formed 

 consists of two somatic chromosomes that were end to end in 

 the spirem. 



Spindle fibers are the result of exosmosis of karyolymph into 

 the cytoplasm, these being formed after the same fashion as the 

 nuclear membrane. The membrane, if it persists, will be a part of 

 the fibers. 



The third contraction which accompanies fiber formation con- 

 sists of a balling up of the chromosomes previous to the complete 

 Alling up of the cavity with fibers. 



Each chromosome is an osmotic System in itself and capable of 

 forming its own weft of fibers after the sap from the nuclear cavit}^ 

 has been exhausted. 



The heterotypic division or the reduction of characters results 

 from a transverse Separation of whole chromosomes. 



During early anaphase the halves of the chromosomes, which 

 originated in presynapsis, separate longitudinally and at each telo- 

 phase approximate end to end, forming the looping spirem of the 

 daughter nucleus, 2 x chromosomes in length. Division in homo- 

 typic mitosis, therefore, results originally from a longitudinal 

 Separation. 



The transverse Separation of the 16 segments during early 

 metaphase of the homotypic mitosis is immediately followed b}^. 

 their pairing. 



To all appearances a typical mitosis is begun, but is varied and 

 dela3'ed for a time by a hetorotypic mitosis as the result of the 

 various contractions, being finally completed in the homotypic 

 division. Jongmans. 



Sax, K., Fertilization in Fritillaria pudica. (Bull. Torrey 

 Botan. Club. XLIII. p. 505—522. 3 Fig. PI. 27—29. 1916.) 



The results obtained from the study of fertilization in Fritillaria 

 pudica are summarized by the author as follows: 



In the mature embryo sac of Fritillaria pudica the egg cell can- 

 not be distinguished from the other two cells of the egg apparatus. 



The „Endospermanlage" extends up between and around the 

 cells of the egg apparatus. 



The pollen tube usually turns along the outer wall of the nu- 

 cellus or embryo sac before entering. At this time the cells of the 

 egg apparatus are all intact. 



The pollen tube practically alwa} r s enters and at least partly 

 destroys one synergid. 



Although a distinct appearance of motility is evident in many 

 male nuclei, the majority do not suggest much motility. 



The male nucleus and the egg nucleus fuse completely before 

 division. 



The upper polar nucleus, with the male nucleus in contact 

 with it, migrates to the lower one, probably by cytoplasmic 

 Streaming. 



The two polar nuclei and male nucleus fuse completely and the 

 subsequent division is normal. 



