130 Dr. R. von Willemoes-Suhm on the [Dec. 9, 



7. As soon as the segmentation begins, large transparent cells are seen 

 separating themselves from the yelk-globules, and increasing in number 

 as the segmentation goes on. 



8. These cells form a blastoderm round the yelk. No primitive streak 

 could be seen ; but its presence is not denied, as the object is not favour- 

 able for these observations. 



9. The blastoderm loses its cellular structure and gives way to a 

 granular skin. On both sides of a longitudinal groove three pairs of 

 appendages begin to be visible. 



10. The test of the ovum extends as the embryo develops. The latter 

 is very likely still enveloped by a thin blastodermic cuticle, which is 

 clearly visible at the ends of tail and antennae, when it comes out. 



11. The development of the Nauplius in the ovum of this Lepas shows 

 very much the same stages as those described by Buchholz in Balanus 

 improvisus. 



II. The Nauplius stages. 



1. The Nauplius of Lepas fascicularis has, when leaving the egg, a 

 length of 0-35 millim. It moults at least five times, and has before 

 throwing off for the last time the Nauplial appendages a length of 

 12 millims. 



2. The first stage of the Nauplius has been seen by Darwin, who 

 describes it, and also by Burmeister. 



3. After the first two moults the Nauplius gets a large dorsal spine 

 and enters a series of stages, one of which has been described in another 

 Lepas by Dohrn as Archizoea gigas. 



4. Reasons are given why Archizoea gigas is nearly certain to be 

 the Nauplius of Lepas australis, a species closely allied to Lepas fasci- 

 cularis, and representing it south of the equator. Archizoea gigas was 

 caught, together with the large Cypricles of Lepas australis, during the 

 * Challenger's ' antarctic cruise. 



5. The tail and the caudal spine of the newly hatched Nauplius are 

 pushed in like the tubes of a telescope, and covered by a thin cuticle, 

 which may be the blastodermic one. The same envelops also the lateral 

 horns, but has not been seen at the end of the appendages. The 

 carapax is as yet quite smooth, with the lateral horns hanging down. 



6. After the first moult the tail and its spines, which have been pushed 

 out, have a considerable length, and the lateral horns are erected. Only 

 a single pair of small spines is to be seen on the carapax. The glands 

 inside are unicellular. 



7. The Nauplius after the second moult has, besides the dorsal spine, 

 a series of processes all round the edges of the carapax, to which the 

 unicellular glands send their ducts. Besides the oesophagus, two glands, 

 which formerly were indicated by an agglomeration of cells, become 

 visible. These glands are very likely those which, in the Cypris stage, 



