EMBRYOLOGY OF CLKPSINE. 225 



and has not hitherto been described. The process can be easily 

 watched if the worm be placed in a small glass containing water, 

 but no plants. The worm is thus compelled to lay its eggs on 

 the glass. The animal takes its ordinary position, attached to 

 the glass by its two suckers, and carries on the usual undulations 

 of the body. While these movements are quietly continued, 

 without any of those violent contractions and twistings seen in 

 C. sexoculata, the eggs are driven forward in the ovary by con- 

 tractions of its walls, aided perhaps by a slight contraction of the 

 hind body. Suddenly the undulations cease; ihe vaginal orifice 

 is directed backwards in consequence of a slight elevation of the 

 segments (somites) that follow the genital segment. The wall 

 of the aperture protrudes ; a single egg appears and is pushed 

 backwards by the protruding orifice as far towards the terminal 

 sucker as possible without moving the head. The eggs follow in 

 tolerably rai)id succession, each being ])laced as far back as 

 possible. After fifteen to thirty eggs are laid, a pause of one or 

 two minutes occurs, during which the undulations are again con- 

 tinued ; and then the eggs are again extruded as before, each 

 time the eggs previously laid being pushed further back by those 

 last deposited. If there are more eggs than can conveniently lie 

 under the expanded body in a single layer, they are placed in a 

 double, and not seldom in a triple, layer. At the end of the act 

 which may last from ten to forty minutes, according to the 

 number of eggs, the eggs lie in quite regular rows, and are held 

 in place by the edges of the body, which are pressed against the 

 object on which the eggs rest. That the eggs come to lie in 

 rows is not due to any skill of the worm in placing them, but to 

 the fact that they are confined between the two nearly parallel 

 edges of the body. The two outer rows are generally shorter 

 than the central ones, as the body tapers somewhat towards 

 either end. 



The eggs are not here enclosed in a sac, but are covered with 

 a transparent fluid substance (probably a secretion of the 

 " Hautdriisen ") which hardens in the course of a few minutes, 

 and thus binds the eggs together and to the object on which 

 they are placed. The worm remains over the eggs for the 

 ])urpose of protection only, till they hatch. The young, soon 

 after exclusion, become fixed to the ventral side of the parent, 

 and are thus borne about till they are fully developed and able 

 to provide for themselves. 



Number and Colour of the Eggs. — There is great variety in 

 the number, colour, and arrangement of the eggs, as will be 

 seen from the following : — 



