110 LEECHES 



3. Egg Laying and Brood Care 



Once fertilization has been achieved the eggs are ready to be 

 deposited in a cocoon. There is often a considerable delay between 

 copulation and cocoon deposition. In the case of the Hirudidae, 



Table 7. Time which may Elapse between 

 Copulation and Cocoon Deposition 



where sperms have been introduced into the vagina directly, we 

 must presume that the sperms are stored and fertilization is 

 delayed, for there is no evidence that the eggs are at an advanced 

 stage in development when they are placed in the cocoon. In other 

 families the delay is only a matter of days and this is presumably 

 the time taken for the sperms to migrate through the tissues after 

 the implantation of the spermatophore. 



There are two kinds of glands contributing material for the 

 formation of the cocoon, those which secrete the outer wall 

 material and those which secrete the albuminous fluid in which the 

 eggs are suspended inside the cocoon. The normal arrangement 

 is for these glands to be distributed over the whole of the body wall 

 in the clitellar region but in a few cases which have been investi- 

 gated, such as Hemiclepsis marginata and Glossiphonia lata the 

 clitellar glands are restricted to a small area round the genital pores 

 on the ventral side of the body. As a result, the method of cocoon 

 formation is considerably modified. Before dealing with it let us 

 consider the more normal method. 



Erpobdellid leeches first prepare a position for cocoon deposition 

 by applying a secretion to the substratum with a ** lapping" move- 

 ment of the anterior sucker. They then place the clitellum over 

 this position and begin to secrete the cocoon. During this process 



