Bigelow. — Nuclear Cycle of Gonionemus murbacbii. 



PLATE 5. 



All figures are magnified 2600 diameters. Figures 92-108 and 120-123 from 

 isolated cells ; figures 109-119 from sections. 



Fig. 92. Spermatid. The interzonal remnants have dwindled to a small sphere. 

 The axial filament extends inward from the centrosome. 



Fig. 93. Spermatid. The centrosome has divided, and the halves lie in the main 

 axis of the cell. Thenucleus has attained its greatest size. The in- 

 terzonal remnants have disappeared, hut there are two arclioplasmic 

 masses lying one on either side of the axial filament. 



Fig. 94. Spermatid. The inner centrosome has nearly reached the nucleus ; it is 

 connected with the outer centrosome hy the axial filament. In this 

 cell the interzonal remnants still persist. 



Fig. 95. Spermatid. The inner centrosome has reached the nucleus and become 

 flattened against it. 



Fig. 96. Metamorphosis of the spermatid. The tail has now grown to a con- 

 siderable length ; the acrosome has appeared at the anterior pole of 

 the nucleus. The chromatin is collected in several masses. 



Fig. 97. Slightly later stage. The acrosome is a sphere of archoplasm. The 

 chromatin has become diffused so that the nucleus is uniformly deeply 

 stained. The two arclioplasmic masses have grown and occupy most 

 of the space between the nucleus and the posterior margin of the cell. 



Fig. 98. The same stage, seen in a plane perpendicular to that of Figure 97. The 

 two arclioplasmic masses nearly cover each other, one lying at high, 

 the other at low focus, and the axial filament running between them. 



Fig. 99. Later stage. The nucleus has assumed a conical form, and shows a 

 deeply stained basal plate. 



Fig. 100. Polar view of this same stage. 



Fig. 101. Still later stage. The cytoplasm has become vacuolated. 



Fig. 102. Adult spermatozoon. The middle piece consists of three separate 

 arclioplasmic masses. 



Fig. 103. Giant spermatid with two centrosomes and two tail filaments. 



Fig. 104. Giant spermatid with three centrosomes and three tail filaments. 



Figs. 105, 106. Later stages in the metamorphosis of giant spermatids, showing 

 evidences of degeneration. 



Fig. 107. Multiple spermatozoon with two nuclei, two centrosomes, and two tails. 



Fig. 108. Multiple spermatozoon with two nuclei, three centrosomes, and three 

 tails. 



Fig. 109. " Resting" stage of oogonium. The nucleolus is compound. 



Fig. 110. Early prophase of oogonium. The karyoplasm has disappeared, and 

 the karyosomes increased in size. 



Fig. 111. Prophase of oogonium, showing contraction. 



Fig. 112. Prophase. The karyosomes have partly condensed to form chromatin 

 segments. 



Fig. 113. Prophase. The nucleolar shell has broken down, but chromatin masses 

 are still attached to the margin of the persistent plasmosome. 



Fig. 114. Later prophase. The nucleolus has disappeared. The chromatin is 

 condensed into segments of the reticulum. 



