r\ iida 



• in-- thoraciques se developpent successivemenl an bord post£- 



sit6t mi nouveau segment form£, une paire de pattes se montre egalement 



mces laterales d un-iit. Quand quatre paires de pattes se ^..ut ainsi deVelopp. 



ments thoraciques (notous que I'ordre de deVeloppement des pattes correspond tout a 



dans l( de I'animal adulte), l'excroissance terminale se change en un abdomen 



in. >ins rudimentaire. 



Morgan has given a little series of essays <>n the Pycnogonida, of which especiall} the last 

 mentioned, entitled : A Contribution to the Embryonalog} and l'h\ logenj of the Pj cnogonids 

 In this Morgan gives the development of Phoxichilidium maxillare [= femoratum 



Rathke?), of Pallene empusa, and of Tanystylum orbiculare. He has more than his two above nn.ii- 

 boned pred< paid attention to the first development of the embryo, an examination that K. rover 



did not enter upon at all, and gives furthermore a verj handsome series of the developmental stages 

 of '.'. . especially the larva of Tanystylum; on the other hand I do not think his represen- 



11 of the larval development of Pallene empusa to be correct In his introduction I.e. p. 2 Morgan 

 many reasons the present paper attempts in no way to give a complete answer from the 

 embi side The very great difficulties of a suitable technique had slowly to be overcome, and 



the time at command prevented a detailed description of the different organs arising from the germ- 

 so that much remains that might be done, but nevertheless his essay is a very important 

 advance in «.ur knowledge of the development of these animals, as also his representation of the 

 structure and development of the eye in the Pycnogonida is rather exhaustive. 



sing now to my own description of the larval development I have to begin with the usual 

 complaint of not having had fresh material at my disposal; but on the other hand the Ingolf-Expe- 

 dition has brought home so rich a material well preserved in spirit that I suppose I shall be able to 

 a more detailed and continuous description of the different stages of development in the larva. 

 I have been able to follow the development for a shorter or longer way in a considerable number .>t 

 mida, belonging to the different families and g. is Nymphon grossipes, Sluiteri, elegans, 



.'hi//, spinosum, macronyx\ Paranymphon spi/iosiiiii x y. Zetes (Eurycyde) hispidus; Pseudo- 

 pallcne circularis and spinipes; Pallene hastata and brcvirostris\ Phoxichilidium femoratum\ Pycnogonum 

 littorale, altogether 7 genera with 15 species. The species, the development of which I have most 

 complete, are Nymphon grossipes, .V. robustum and Pseudopallene circularis, of which three species the 

 first and the last are those that have been particularly examined by Kro\er; but besides corrobo- 

 rating 1 ids statements and drawings il have partly examined his original pieces) I have also 

 n able to increase and partly to cornet some of them, which corrections especiall} appl) to Pseu- 



The segmentation, yolk-division, of the Pycnogonid ovum is complete, some- 

 times equal, sometimes unequal. 



I this thesis I must refer to Morgan, Contrib. EmbryoL, 1891, and I 



have nothing t.. add. It is, I think, t<> be supposed, .is Morgan does I.e. p. 23, that the difference 



;.d and unequal segmentation, which latter is also continued in the difference between 



li .1 Bpinipes in stead ..1 spinosum. 



