114 



LEECHES 



elongated ectodermal cells placed near the anterior end of the 

 body in the mid-ventral line. The embryos, which at this stage 

 break free of the thin-walled cocoon, become arranged in a single 

 layer with their attachment organs directed upwards and each of 

 these then becomes interlocked with elongated epidermal cells 



(j) 



Fig. 66. Egg laying by Glossiphonia lata, (a), (b) formation of 

 a cavity on the ventral side of the body; (c) to (g), secretion of a 

 saclike cocoon by a ring of clitellar glands round the genital 

 pore and extrusion of the eggs into the cocoon ; (h), (i), cocoon 

 moved to a posterior position for brooding; (j), appearance of 

 cocoon. From Nagao, 1958. 



which form a kind of socket on the parent's ventral body wall. 

 It has been suggested that a transfer of nutriment takes place at 

 this stage but on the whole this seems unlikely as the embryo is 

 well provided with yolk and the egg membrane is interposed 

 between embryo and parent. 



