472 F. A. PUTTS. 



egg-production. In the Cambridge specieis of Rliabditis, on 

 the other haud, the early sterility was certainly due to the 

 extremely small number of spermatozoa. The length of the 

 ovary was proportionately as great ;is in other species of the 

 genus. 



Rliabditis gurneyi, in contrast to tlie two species last 

 discussed, is a free-living hermaphi-odite nematode which has 

 departed from the protandrous hermaphroditism, which we 

 regard as the earliest development from the bisexual state. 

 In consequence it far surpasses others of its kind in fertility. 

 The spermatozoa are of unusual size, and possibly because of 

 the difficulty of providing sufficient space to store a sufficient 

 number at once, they are produced alterniitely with eggs 

 throughout a great part of the period of reproductive activity. 

 As a result of this adaptation each individual is capable of 

 laying as man}^ eggs as a bisexual female, wliich frequently 

 has its supply of spermatozoa replenished by copulation. 



It must be remembered that in many cases the hermaphro- 

 dites of this species only produce unfertilised eggs in the 

 initial period of oviposition which represent a total loss to 

 the organism. When once this critical period has been 

 passed, and a sufficient supply of spermatozoa established, 

 fertile eggs are produced at the rate of 60-80 each day, or 

 distinctly faster than in the case of Diplogaster maupasi 

 and others. 



For figures to illustrate the fertility of Rhabdi tis gurneyi 

 the following case is given. From the offspring of a single 

 individual six immature hermaphrodites were selected. 

 When maturity was reached the eggs laid every twenty-four 

 hours Avere counted, and the parent removed to a fresh 

 culture drop in the manner described above for Diplo- 

 gaster maupasi. The dates in each case mark the period 

 over which oviposition continued. 



(a) September 6th-17tli, 525 fertile eggs. 



(b) „ 7th-17th, 686 „ 



The figures here are not complete, for the cultui-e dried up 

 while the parent was still laying fertile eggs. When 343 had 



