THE NUCLEAR STRUCTURE AND THE SPORU- 
LATION OF AGRIPPINA BONA STRICKLAND. 
By KENNETH R. LEWIN, B.A. 
Assistant to the Quick Professor of Biology. 
{From the Quick Laboratory, Cambridge.) 
(With Plate XVIII and 8 Text-figures.) 
Introduction. 
Agrippina bona, a gregarine parasitic in the gut of the larva of the 
rat-fiea Ceratophyllus fasciatus, was first described by Strickland in 
1912. His account of the sporulation of the gregarine was so curious 
that a more detailed investigation has been undertaken, which has given 
rise to the pi’esent paper. The woi'k lias been done in the Quick 
Laboratory, under Professor Nuttall, to whom I wish to express my 
thanks for the interest he has taken in my researches, and for his 
constant encouragement. 
Throughout the winter, the results that were obtained, although 
they did not confirm Strickland’s account, pointed without exception to 
the origin of the gamete nuclei from chromidia. In the latter part of 
May, and in June, every cyst fixed in the stages preceding gametogenesis 
has shown clearly phases of the mitotic divisions which in almost all 
gregarines give rise to the gamete nuclei. I can only conclude that 
either all my earlier preparations of these stages were made from abnor¬ 
mal cysts, or that the gamete nuclei may be formed in one of two ways: 
by chromidiation, or at the end of a series of mitoses. As to the 
degeneration hypothesis, I must state that the score or so of cysts that 
were kept in hanging drops in the winter proceeded without exception 
to form spores, and even in roughly-sealed preparations under the 
