hargitt: pennaria tiarella and tubularia crocea. 195 



In Tubularia crocea the oogonia are all alike; but in the oocytes, 

 even before growth begins, a difference is apparent, the chromatin in 

 the nucleus being either (1) in the form of a spireme or (2) scattered 

 in grains along a network. The oocytes which possess a nuclear 

 spireme begin growth at once, the most of those with a diffuse net- 

 work serve as food, though if they escape this fate they seem to be able 

 later to form egg cells. The cause of this differentiation seems to be 

 better nourishment, as the oocytes near the spadLx are most often the 

 ones which first begin to grow. 



The cell which begins to grow absorbs the surrounding cells by one 

 or another of various methods. The nucleus of this growing oocyte 

 is commonly believed to become the germinative vesicle, while the 

 nuclei of the absorbed cells are used as food at once, or remain in the 

 cytoplasm as yolk bodies, "pseudo-cells." However, Allen (:00, p. 

 300) says in regard to Tubularia (Parypha) crocea: "... .the nuclei 

 of the growing cells disappear at an early stage, so that only the 

 nuclei of the smaller cells persist." "It thus becomes impossible to 

 tell which is the controlling cell." This is exactly the opposite of 

 what I find in the same species, for in my preparations the nucleus 

 of the growing oocyte is always present and easily distinguished, 

 because of marked differences between it and the degenerating nuclei 

 of the absorbed oocytes. 



2. Synapsis and Reduction. — In Tubularia after the last oogonial 

 division, and before the growth of the primary oocyte begins, the 

 chromatin of the nucleus is in the form of a spireme, which soon takes 

 the form of loops showing a definite polarity, the open ends of the 

 loops apparently being attached to the nuclear membrane. This 

 condition seems to correspond to similar polar arrangements of the 

 spireme in the synapsis stage of other metazoa. A, synapsis in Coelen- 

 terata has been described in spermatogenesis by Guenther (:04) and 

 Downing (:05) for Hydra, and by Bigelow (:07) for Gonionemus. 

 Stschelkanowzew (:06) figures nuclei of spermatocytes in which the 

 chromatin appears to be in a contraction stage or polar arrangement, 

 but does not so describe it. The characteristic condition is such as 

 might result from a contraction into a dense mass. Bigelow thinks 

 that in Gonionemus this is artificial. Trinci (:07) has described a 

 synapsis as occurring during the oogenesis of several Hydromedusae. 

 He also shows a contraction phase, though in his figures the chromo- 

 somes still show a rather definite polarity after the contraction. 



After the contraction Guenther found a reduced number of chromo- 

 somes, while Downing thinks the reduction occurs in the telophase of 



