No. I.] THE EMBRYOLOGY OF LIMULUS, 41 



and from one or two to five spherical and deeply staining nucle- 

 oli. There is no ' yolk nucleus ' like that described in certain 

 Arachnids. 



As will be seen, the foregoing description differs in toto from 

 Packard's brief account and figures ('80, p. 39, PI. IV, Figs. 8, 

 8^). In fact, I cannot determine what he had under the micro- 

 scope. If I understand Gegenbaur ('58) aright, the eggs in his 

 specimen 1 project into the lumen of the ovarian tube, a differ- 

 ence possibly explicable on account of the mature condition of his 

 material. He was farther unable to recognize any membrane 

 around the ^g^ aside from the epithelial cuticle of the ovarian 

 tube. In other respects there is no discrepancy between our 

 accounts. 



Making comparisons now with the Arachnida, we see no little 

 similarity in the structure of the ovary and the relations of the 

 ova. Metschnikoff ('71, pp. 207-208, PI. XIV, Figs, i and 2) 

 and Laurie ('90, pp. 108-111, PI. XIII) describe and figure 

 almost the same condition in the scorpion. The ovary consists 

 of the same epithelium and tunica, and the eggs, as they increase 

 in size, come to lie between these two layers. The differences are 

 that in Limulus each Q.g^ is not enveloped in a separate follicle ; 

 but in the scorpion, where the eggs are few, such is the case. 

 In Limulus the epithelium does not form such a well-marked 

 "stalk" connected with the egg as in the scorpion; and the 

 cells of this stalk are columnar, not stratified. Closely similar 

 resemblances can be traced with the Araneida, as epitomized by 

 Ludwig ('75) and the Acarina (Pagensticher, '60-'6l). In the 

 Crustacea, on the other hand, a similar condition is not found, 

 there being nowhere an ovary with a similar constitution. In 

 short, so far as my observations on ovigenesis go, Limulus 

 agrees well with the Arachnida and contrasts strongly with the 

 Crustacea. 



Early Development. 



The eggs of Limulus, as they come from the oviduct, vary con- 

 siderably in size and shape. They are usually more or less oval, 



^ Twenty-five German inches long. Gegenbaur is in doubt about his specimen. 

 In appearance it was clearly Z. molliiccanns, but so far as he was able to find out it 

 came from the West Indies. As L. polyphemns and L. molluccanus are easily distin- 

 guishable, it is possible that a mistake was made in locality. 



