No. 500] NOTES AND LITERATURE 



549 



younger stages when the nucleus occupies a central position in 

 the zoospore origin. 



Yamanouchi 2 lias given an account of spermatogenesis for 

 Xephrodium in one of a series of papers dealing with the life 

 history and apogamy of this fern. The hlepharoplasts arise 

 de novo just before the last mitosis in the antheridium. that 

 mitosis which different iates the spei'in mother cells. They are 

 first seen as small bodies lying within the cytoplasm on opposite 

 sides of the nucleus and at a considerable distance from it; they 

 appear suddenly, as differentiated by staining, and are unex- 

 pectedly large. The hlepharoplasts move towards the nucleus 

 and during the final mitosis take positions near the poles of the 

 spindle. Sometimes the hlepharoplasts may lie exactly at the 

 poles of the spindle, and consequently suggest relationships to a 

 centrosome, but this is not often, and there can be no such 

 relationship in Xephrodium because centrosomes are not present 

 in the earlier mitoses of the antheridium or at any other period 

 of the life history. 



As a result of the final mitosis in the antheridium each sperm 

 mother cell receives one of the two hlepharoplasts close by the 

 side of the daughter nucleus. The nucleus in the sperm mother 

 cell now increases in size and the hlepharoplast. at first spherical, 

 changes its form. It enlarges and is flattened somewhat against 

 the side of the nucleus and begins to elongate. The outline be- 



A complicated development follows for both the nucleus and 

 the hlepharoplast. One end of the hlepharoplast grows wedge- 

 shaped and is loosely applied to the nucleus while the other end 

 remains pointed and extends around in very close contact with 

 its surface. The nucleus meanwhile changes its form, becoming 

 a coiled structure and the elongating hlepharoplast follows the 

 coils in the form of a narrow band, which reaches to the end of 



coil. In this manner the coiled and spiral form of the sperm 

 is developed, and by this time numerous cilia have grown from 



