1907.] NATURAL SCIENCES OF PHILADELPHIA. 127 



resemblance in size ami stainiiif!; reaction to many of the cells compos- 

 ing the lateral walls of the ascending liml) of the oesophagus, in addition 

 to the fact that, in those individuals in which these amoeboid cells 

 occur, they arc always found in the neck region in a normal condition, 

 seems to point to the oesophagus as their place of origin. 



The function of these cells is somewhat problematical. Their 

 amceboid and phagocyte-like api:)earance, the frequent occurrence of 

 inclusions, and their degeneration within the ectoderm near the 

 exterior, point strongly to the conclusion that they perform the func- 

 tion of phagocytes. This conclusion attains a considerable degi'ee of 

 jirobability in the light of the researches of Schaeppi (1894) and Graf 

 (1898) on polychsetous annelids and leeches respectively. In repre- 

 sentatives of both these groups there are found in the body cavity 

 amoeboid cells ("Chlorogogen," "Excretophores"), whose function is 

 to ingest and remove waste matters. Moreover, Graf found that in 

 the leech these cells sometimes degenerated in the epidermis. There 

 seems, therefore, much reason to believe that the amoeboid cells in 

 Dinophilus are also "excretophores." 



6. Sex Organs. 



Ovary. — The ovary in its position and general structure resembles 

 that of Dinophilus apatris and Dinophilus gyrociliatus, as described by 

 Korschelt (1882) and Repiachoff (1886) respectively. It lies on the 

 ventral side of the alimentary canal, occupying the concavity formed 

 by the junction of the stomach and intestine, and commonly fills up 

 this space and crowds the intestine towards the dorsal side. The 

 ovary consists essentially of three parts: the oogonia; the oocytes; and 

 the peritoneal sac enveloping the whole. 



The oogonia form a pyriform mass of closely packed cells (fig. 21, 

 cog.), its smaller end directed caudad. The apex of the oogonial mass 

 is formed of the younger cells, wiiich are still in a state of multiplica- 

 tion. In fig. 21 a zone of dividing cells is seen extending across this 

 portion of the ovary. Beyond this zone the oogonia may be seen to 

 increase gradually in size toward the anterior end of the oogonial mass, 

 where the oogonia, having completed their growth, become oocytes. 

 The manner of formation of the large ova which are destined to form 

 the female individuals, by the fusion together of several oogonia, was 

 first noted by Schimkewitsch (1895), and has been more fully described 

 by Conklin (1906) for the form under discussion, and by von Malsen 

 (1906) for D. apatris, and will not be dwelt upon here. The cytoplasm 

 of the oogonia is finely granular, and stains more or less densely, 



