EEPOET ON THE PYCNOGONIDA. 131 



specimen is a male ; even in very young females at least a trace of the ovary is always 

 to be observed in those joints. 



According to Dohru the female glands are disposed in the same way as the testis, 

 with the only difference, that in the ovaries of most species, the lateral excres- 

 cences which penetrate the legs and often force their way into the penultimate joint, 

 are the only parts which develop mature eggs. 



What I happened to observe agrees almost completely with Dohrn's description. 

 I perfectly believe, however, that the occurrence of a part of the ovary in the body of a 

 Pycnogonid is rather rare, because, as a rule, only the lateral excrescences remain. 

 No doubt this must be considered as a secondary condition ; and seeing that, so far 

 as I could ascertain, it is the rule in all the species of Nymphon, my original opinion, 

 that the genus Nymjjhon, of all the genera of Pycnogonida, resembled most the 

 hy|3othetical ancestors of our group, was severely shaken. 



The genus Colossendeis affords a beautiful example of the original condition of the 

 ovary. I examined a specimen of Colossendeis leptorhynelms, Hoek. A transverse 

 section of the body showed the place occupied by the ovary, and convinced me of the 

 exactness of Dohrn's assertion. However, as in the case of the testis, Dohrn's observa- 

 tion is incomplete in one respect ; there are not two ovaries, but only one. Immediately 

 in front of the abdomen the two lateral parts are united by a cross-piece, and so the 

 ovary has the very same shape as the testis, viz., that of a U with long upstrokes. 

 That it occupies also the same position in the body as is the case with the testis, is clearly 

 seen in fig. 14, Plate XXL, which is a drawing of a transverse section of the body. In 

 0. the ovary is shown placed above the intestinal ti'act and its excrescences which pene- 

 trate the legs. The dimensions of the eggs in that part of the ovary which is situated 

 in the body are, at least in this species, the same as of those eggs which are found in the 

 thighs of the legs. The lateral excrescences penetrate all the legs, and in the specimen I 

 studied reach the sixth joint. This, most probably, will greatly depend on the state of 

 maturity of the animal. I often found the eggs only in the thigh, but often also {Han- 

 nonia typica, Hoek, PI. XIV. fig. 11, e.g.) the eggs are found as far as the end of the 

 second tibial joint. The ovary is always placed dorsally to the intestinal tract, which 

 is also the case with those animals which have only the lateral excrescences left, and 

 thus show several ovaries. 



The structure and the formation of the ovarian eggs I will describe further on. In 

 regard to the way in which the eggs are laid, I had the good fortune to observe the 

 copulation of a male and female Phoxichilus laevis, Grube, when I was, last summer, 

 in the zoological station of Professor H. de Lacaze-Duthiers at Roscoff. The eggs 

 are fecundated the moment they are laid, and the copulation, therefore, is quite 

 external, brought about by the genital openings of the two sexes being placed against 

 each other. Half an hour after the beginning of copulation, the male had a large 



