26 



ART. 4. — EKITARO NOMÜEA : 



tf : \î)- 



-int 



pvra 



Fig. 18. 



L. gotoi. Part of a cross section 

 through segment VIII, showing 

 the relation of the parietovisceral 

 muscles to the internal organs. 

 x 150. dv — dorsal vessel, siv — 

 supraintestinal vessel, ht — heart, 

 int — intestine, nc — ventral nerve 

 cord, bw — body wall, pvm — 

 parieto-visceral muscle. 



next lie the longitudinal muscle fibres 

 united into bundles and last comes the 

 intima, which lines the whole interior 

 of the heart. The longitudinal muscle 

 seems to act as valves at the ends of 

 the hearts. The circular muscle layer 

 of the heart is connected to the body 

 wall by branches of the parieto-visceral 

 muscles. 



8. Genital system. 



The organs which are to be 

 described in this section are the testis, 

 the sperm-sac, the sperm-duct, the 

 spermatheca, the ovary, the ovisac, and 

 the oviduct. 

 1). Testes. These are attached to the posterior face of 

 septum IX/X and provided with a very thin membrane. 



2). Sperm-sacs. In young specimens, in which the sperm- 

 sacs have not been formed, the germ cells, liberated from the 

 testes, aggregate on the dorsal side of the intestine and are 

 found attached to the posterior face of septum IX/X. They are 

 richly supplied with cœlomic commissural vessels in segment X. 

 But after the formation of the sperm-sacs the sperm-cells are 



always found in them, and go through the 

 stages of spermatogenesis there. 



The sperm-sacs are outgrowths of the 

 septa of the tenth segment. The anterior 

 sperm- sacs originate in a pair from the 

 anterior septum and lie in segment IX, 

 while the posterior one is formed by the 

 posterior septum and extends backwards. 

 Fi £- l9 - The posterior sperm- sac, when fully grown, 



L. gotoi. Diagram showing traverges the ent j re Wfa f Segment XI, 

 an unequal development of ... 



the anterior sperm-sacs. and is telescoped into the ovisac, sometimes 



