34 Papers from the Marine Biological Laboratory at Tortugas. 
IPEATES 2: 
Fic. 25. Very late telophase; mid-body prominent. 
Fic. 26. Resting-stage of the final order of secondary spermatogonia, showing a 
chromatin nucleolus (“accessory chromosome”). 
Fics. 27, 28, 29, 30, 31. Successive stages in the prophase of ensuing mitosis; acces- 
sory chromosome in figure 30 distinctly bipartite. 
Fics. 32, 33. Equatorial plates each with 35 chromosomes. 
Fic. 34. Two spindles at metaphase, showing accessory chromosome splitting at the 
right of lower spindle. 
Fic. 35. Early anaphase of similar cell. 
Fic. 36. Later anaphase. 
Fic. 37. Telophase stage, showing two pairs of lagging chromosomes. 
Fics. 38, 30, 40, 41, 42. Successive stages in the telophase of final secondary sperma- 
togonial division. 
Fics. 43, 44, 45. Still later steps in the telophase of similar division; mid-body con- 
spicuous in each spindle; figure 44 shows persistence of accessory chromo- 
some as a body of sharp contour and deep-staining capacity among the 
pale-staining, irregularly shaped ordinary chromosomes. 
Fic. 46. Nucleus of primary spermatocyte in resting-stage. Reticulum delicate and 
only very slightly chromatic. Accessory chromosome very close to nuclear 
wall. This phase is of very brief duration, as also the following one. 
Fic. 47. Early growth-period of primary spermatocyte; nuclear reticulum more highly 
chromatic and with several karyosomes. 
Fic. 48. Late growth-period; chromatin in form of close-meshed network of broad, 
mossy, lightly-staining threads. Accessory chromosome closely attached to 
nuclear wall. Amount of cytoplasm very small. 
Fics. 49, 50, 51, 52. Successive stages in the presynaptic phase of the growth-period. 
he accessory chromosome has become an elongate, club-shaped structure 
attached at its narrower end to the presynaptic chromatin thread; the 
latter in the form of a close-meshed lattice-work. Figure 50 shows two 
such cells still connected by cytoplasm of mother-cell. In figure 52 the 
accessory chromosome is beginning to split longitudinally. 
PEATE? 3: 
Fics. 53, 54, 55, 56, 57, 58. Stages of synapsis. X=synaptic point. Accessory 
chromosome is closely applied to nuclear wall; frequently it is split as 
in figure 57. Figures 57 and 58 may be identical with the “ bouquet 
stage” of Eisen. 
Fic. 59. Postsynaptic stage. Chromatin in form of an irregularly loosely-meshed 
network of broad, mossy threads, which give indication of a longitudinal 
split. The accessory chromosome is close to the wall; the cytoplasm is 
still scant. 
Fic. 60. Resting-stage of postsynaptic period (stained in methyl green). The acces- 
sory chromosome has the appearance of a hollow sphere. 
Fic. 61. Resting-stage (stained in iron hematoxylin). Nuclear reticulum very delicate 
and very slightly chromatic. Accessory chromosome solid and attached 
to nuclear wall. 
Fic. 62. Resting-stage in which the reticulum is more chromatic; contains karyosomes 
and has a bipartite accessory chromosome. 
Fic. 63. Early prophase of heterotypic mitosis; nuclear reticulum consists of coarser 
and more highly chromatic threads; accessory chromosome in form of 
a deeply chromatic sphere some distance from nuclear wall. The sparse 
cytoplasm contains several small masses of eliminated chromatin. 
Fic. 64. Later prophase; accessory chromosome clearly double. 
Fic. 65. Still later prophase; pale-staining, mossy spireme partially segmented and with 
indication of a longitudinal split. 
Fics. 66, 67, 68, 69, 70, 71. Stages in the prophase of the heterotypic division. The 
accessory chromosome (a) assumes various shapes, but always retains 
its definite contour and intense staining capacity. Several of the ordinary 
chromosomes, which stain only slightly at this stage, are in the form 
of tetrads. 
Ries: 72) 72. Later prophases ; all the chromosomes have similarly sharp contours and 
intense staining capacity. Figure 73 has a ring-shaped tetrad and dumb- 
bell-shaped accessory chromosomes (a). 
