Japanese Tricladida Maricol-i. 



33 



■"</l'S 



species tlioy are closely opposed to the brain, wJiile in SL tngono- 

 cephala tliey are situated a little farther behind the brain. 

 Besides, no special organ known as paraovarium is present. 



The ovary is a solid mass of germ cells in several stages of 

 development and is enclosed by a delicate membranous capsule of 

 connective tissue, the tunica propria, which exhibits no sign of 

 cellular structure or of distinct epithelium; the unripe ova are 

 found in the anterior part and the more developed ones in tlie 

 postero-lateral part, 

 whence the oviduct 

 takes its rise. Be- 

 tween tlie ova til ere 

 exists a mass of pro- 

 toplasm in which 

 small nuclei are em- 

 bedded. As was 

 mentioned by Ijima 

 (20), Chkhkoff (11), 



V. Graff (24), Böhmk; 



and others, these 



protoplasmic masses 



probably represent 



undeveloped germ- 

 cells. It may be that 



these act as nutritive 



cells, the products of 



which pass into the 



ova. Judging from 



the relative size, the 



ova become gradually larger and larger in all the dimensions. 



The nuclei become remarkably large and vesicular, the chromation 



granules become more and more undefined, and a distinct 



nucleolus makes its appearance in each nucleus. In the mature 



state the protoplasm is very finely granular and very conspicuous 

 around the nucleus. 



VlteUhie Gland.— -The vitelline glands are represented by eel- 



Text fig. 6. Copulutory organs of Ectoplana limuli 

 in sagittal section. Diagramuiati' . 



Index letters as in text figg. 1, 3, 4 and 5. 



