Bennet Mills Allen 137 



Beard, oo, 02, 03, Eigenmanu, 91, Woods, 02, and others; but I do 

 assert that the proof of such an assertion has not yet been furnished. 

 The development of the sex cells must be followed from the earliest 

 embryonic stages to the period of sexual maturit}^, before one can prove 

 that the cells under consideration are the only ones that give rise to 

 the sex products, or that they give rise to them at all. 



5. MoRPHOLOC4iCAL Eelationships. — The morphological significance 

 of the sex gland structures may be expressed in terms of the biogenetic 

 law somewhat as follows : The genital ridge represents a primitive con- 

 dition in which the sex gland extended along the entire length of the 

 mesonephros. In this sex gland, the gonads appeared in the form of 

 tubules or vesicles opening into the body-cavity in the case of both ovary 

 and testis. It was impossible, in this piece of work, to determine whether 

 there is any segmental arrangement of the sex cords in the forms studied. 

 Such, however, would most probably be the condition in the primitive 

 t^-pe. 



The evaginations from the Malpighian corpuscles no doubt represent 

 the " segmental strange," " genital kanale," etc., of those authors who 

 have worked upon the development of the sex glands in the Anamnia. 

 In the Amphibia, for instance, they have a truly segmental arrange- 

 ment, according to Hoffman, 87, Spengel, 76, Semon, 92, while Hoff- 

 man, 89, Braun, 77, Mihalkovics, 85, Semon, 87, Weldon, 85, show a 

 like segmental arrangement to occur in the Eeptilia. Much might be 

 said in this connection, as the literature upon the subject is quite rich 

 in suggestive facts. 



According to Shreiner, there are 2 to 3 glomeruli in each somite of 

 the pig. My own work has shown that a connection takes place between 

 the rete tissue and those glomeruli with which it comes in contact, 

 there may be as many as three evaginations called forth from a single 

 glomerulus or there may be none at all. For these reasons we cannot 

 assert a strict homology between these evaginations and the " segmental 

 strange " of the Anamnia, yet the former probably represent a modi- 

 fication of the same process, as that by which the formation of the latter 

 are formed. 



Returning to the subject of the genital ridge as a whole, it would seem 

 fair to conclude that the sex cords which in the ancestral forms lay 

 posterior to the present limits of the sex gland, have disappeared. The 

 rete tubtiles would represent sex cords anterior to the sex gland that 

 had retained more or less of their ancestral condition, but have become 

 modified to meet the requirements of their function as efferent ducts 

 for the male sex products. The union of the rete tubules with the sex 

 11 



