GERM CELLS IN PEDICELLINA AMERICANA 41 



of V's which later by the union of the free ends, form a ring. 

 By further concentration, this figure may become a dumb-bell- 

 shaped structure {Peripatus, BracJiystola^ etc.). In Pediccllina^ 

 as has already been pointed out, there is no continuous spireme 

 and the early chromosomes are V's, in all regards like those of 

 the second t3^pe, but by the opening up of the angle and the 

 subsequent continuity of the univalent rods, are converted into 

 the parallel bivalent bars of the first type. Pedicellina thus 

 presents conditions that bridge over the two classes and shows 

 clearly that these are really variations of one main type of chro- 

 matin formation. 



In view of the foregoing facts, it may be questioned whether 

 a continuous spireme really ever occurs even in the Copepods, 

 as described by Hacker, '95. The work of Riickert, '94, does 

 not show a continuous spireme at any point in oocytic develop- 

 ment. The parallel bivalents appear in the very early oocytes 

 and arise not through any process of segmentation, but rather 

 by the moving apart, as growth proceeds, of the separate ele- 

 ments within the much crowded nuclei of the earliest period, 

 i. €., of the "synapsis" stage (cf Figs. 1-2, PI. XXI, '94, 

 Anat. Hefte). Hacker's own figures are far from proving his 

 contention, and are much more favorably adapted to an inter- 

 pretation in line with what is observed in the other forms, viz., 

 Peripatus, Brachystola and particularly Pedicellina. Thus neither 

 Figs. 5 nor 6, PI. XIV, A. M. A., '95, representing the first 

 type, /. e., where segmentation occurs before concentration, nor 

 Figs. 16-17, PI- XV, of the second type, show continuous spi- 

 remes. They are more probably secondary appearances which 

 have arisen by the apposition end to end of a considerable 

 number of the parallel bivalents. This supposition is much 

 strengthened by the conditions presented in his Figs. 7-1 1, PI. 

 XIV, where this apposition actually occurs to form not a con- 

 tinuous spireme, but rather, what Hacker designates as an 

 ophiuroid figure. The author looks upon these as secondary 

 unions, in contrast to the continuous spiremes which are pri- 

 mary structures ; but he gives no evidence for this distinction. 

 The eggs are of the same age and the nuclei are in the same 



