123 



It is still, of course, an open question whether the present example 

 is to be regarded as a reversion or as a casual variation which 

 happens to simulate such a reversion. However, the fact that similar 

 variations have been observed three times in the last three years is 

 certainly in favour of the view that we have here a true reversion 

 to a fish-like ancestor and from this point of view I think the variation 

 possesses considerable interest. 



June 16, 1900. 



Nachdruck verboten. 



A Variation in tlie Grenital Organs of Luml)ricus agricola HoFFM. 



(Work done in the Zoological Laboratory of the University of Michigan, 

 Jacob Reighard, Director.) 



By Raymond Pearl. 



With one Figure. 



The variation here described was found by a student in Biology 

 at the University of Michigan in an earthworm which he had begun 

 to dissect. The specimen was brought to me in a practically uninjured 

 condition, and upon examination such peculiar relations were found as 

 to make a thorough study of the case desirable. The variation is 

 apparently anomalous, none exactly like it having been recorded so 

 far as I am able to discover, and it seems to throw some light on 

 teratogenetic problems. 



The specimen was first dissected and then serial sections of so- 

 mites 9 to 17 were cut, the study of the sections confirming the 

 points made out by the first method. 



1. External Characters. 



The openings of the genital organs on the right side of the body 

 are in their normal positions, i. e. the openings of the seminal receptacles 

 between somites 9 and 10, and 10 and 11 ; oviducal opening on so- 

 mite 14 and that of the vas deferens on somite 15. 



On the left side of the body there is in addition to the usual 

 member of genital pores an extra one between somites 11 and 12, 

 lying directly behind the openings of the normal seminal receptacles 

 on that side. This pore is shown by dissection to be the opening 

 of a supernumerary seminal receptacle. The openings of the oviduct 

 and vas deferens on the left side are each one somite posterior to 

 their normal position, i. e. on somites 15 and 16 respectively. 



