1904.] 



NATURAL. SCIENCES OF PHILADELPHIA. 



211 



The original object of this paper was a discussion of the reproduc- 

 tive organs, ovogenesis, spermatogenesis and embryological develop- 

 ment of Planaria {luguhris). The discovery that it is not P. luguhris 

 but P. simplissima Curtis renders further discussion of the reproductive 

 organs unnecessary, and I shall therefore confine my attention to a 

 study of the germ-cells and the embryology of this species, which pre- 

 sents some peculiarities not fully described by Ijima ('84) and Hallez 

 (79). 



Fertilization. — Copulation has not been observed in this species, 

 but there is every reason for supposing that it occurs, for spermatozoa 

 are found only in the vasa deferentia, the lumen of the penis, the 

 uterus and the oviduct. In nearly every specimen the anterior end 

 of the oviduct is crowded with spermatozoa (PI. XIII, fig. 1, od), while 

 only occasionally one is found in the posterior part of the duct or in 

 the uterus. The spermatozoa are never found among the oocytes in 

 the ovary, and it is probable that each egg is fertilized as it enters 

 the oviduct, for the spermatozoon is always found in the eggs of a 

 forming capsule, and no spermatozoa are found among the eggs and 

 yolk. 



I should therefore agree with Ijima in regarding the uterus as a 

 gland for forming the cocoon shell, and not as the 

 place where fertilization occurs (Hallez), or as a re- 

 ceptaculum seminis (Kennel). 



When an egg-capsule is forming, the antrum, 

 uterus and the tube x (fig. C) are all thrown into 

 one chamber, which is filled with eggs and yolk- 

 cells, the penis being pushed back against the 

 anterior wall of the antrum (fig. E) and the antrum 

 l^eing separated from the pharynx-chamber by so 

 thin a layer of tissue that it is often broken through 

 in fixed specimens, and yolk-cells are found in the 

 pharynx-chamber. 



Ovogenesis. — The early stages in the development 

 of the oocytes evidently should be studied in the 

 summer after laying-time, for the ovaries are practi- 

 cally unchanged in appearance from October to lay- 

 ing-time in April. Figure 1, drawn from a section 

 cut in November, shows nearly all of the odcj^tes 

 in the same condition as in sections containing the 

 first maturation-spindle (cut in April and May). 

 The cytoplasm of the oocytes stains deeply with hsematoxylin and 



Fig. E. Median 

 longitudinal sec- 

 tion through an 

 individual con- 

 taining an egg- 

 capsule (c). od= 

 oviduct. p= 

 penis 



