182 bulletin: museum of comparative zoology. 



ent eggs of the same size, the reticulum retaining the deeply staining 

 capacity in some for a long time. Just before the time of polar-cell 

 formation, however, the germinative vesicle shows a minimal affinity 

 for basic stains. 



During the changes last described there occurs a great increase in 

 the size of the nucleus. Figures 29-46, all drawn to the same scale, 

 make evident this growth. In the full grown egg the germinative 

 vesicle is, however, very small in proportion to the size of the egg, as 

 may be learned from Plate 7, Figures 55 (a nearly full grown egg) 

 and 56 (one that has completed its growth). The failure of certain 

 observers to find the germinative vesicle is partly due, without doubt, 

 to its relatively small size and its lack of affinity, at this time, for 

 nuclear stains. 



Almost as soon as growth begins, though sometimes much later, 

 the cytoplasm, which at first is compact and finely granular, becomes 

 vacuolated or alveolar, and this condition continues throughout its 

 subsequent development. In the early stages of growth, even when 

 the egg has increased to one-quarter of its final size, no "pseudo-cells" 

 are present. Gronberg ('98) described the same condition in young 

 ova of Tubularia coronata, and thought it was an indication that the 

 increase in the size of the ovum was due to the formation of vacuoles 

 in the cytoplasm, no oocytes, in his opinion, being absorbed until later. 

 But in Tubularia crocea, at least, another explanation is more satis- 

 factory. The oocytes which are situated near the spadix and often 

 retain their original position till a late stage, are usually the ones which 

 first show signs of growth, and they probably secure nourishment 

 from the spadix. Moreover, in Tubularia crocea, oocytes are absorbed 

 by the egg during its early growing period, as well as at later stages. 

 The absence of "pseudo-cells" is a sign of complete digestion of 

 absorbed oocytes, rather than of an increase of the ovum by simple 

 vacuolization of the cytoplasm. Evidence of this is found in the fact 

 that there are oocytes of many times their original size in which the 

 cytoplasm is still granular or only slightly vacuolated. The presence 

 of "pseudo-cells" is, in part, an indication of the storing of food matter 

 for future use. The absence of "pseudo-cells" is characteristic of 

 the eggs of Pennaria through their entire growth period, as Hargitt 

 (:00, :04'=) has shown; yet during this period the surrounding oocytes 

 are being absorbed, and they furnish the food for the growing ovum, 

 precisely as in Tubularia. 



The oocyte, though at first nearly spherical or ellipsoidal and having 

 regular outlines (Plate 5, Fig. 38), later sends out blunt pseudopodia, 



