138 PROGRESS OF MICROSCOPICAL SCIENCE, 



refractive granules may be sceu here and there among the yelk- 

 globules. The ovum is oval in form. 6. The segmentation is very 

 irregular, but seems to be complete. 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 bo seen ; but its presence is not denied, as the object is 

 not favourable 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 antenna?, when it comes out. 



11. The develoj)ment of the Nau'plius in the ovum of this Lepas shows 

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

 impi-ovisus. 



II. The Nauplius stages. 



1. The Nauplius oi Lejxis fascicular is has, when leaving the egg, a 

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

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

 12 millims. 2. The first stage of the Nauplius has been seen by 

 Darwin, who describes it, and also by Burmcister. 3. After the first 

 two moults the Naupilius gets a large dorsal spine and enters a series 

 of stages, one of which has been described in another Lepas by Dohrn 

 as ArcJiizoea gigas. 4. Keasons are given why ArcMzoea gigas is 

 nearly certain to be the Nauplius of Lepas australis, a sj)ecies closely 

 allied to Lepas fascicularis, and representing it south of the equator. 

 ArcMzoea gigas was caught, together with the large Cypridcs of Lepas 

 australis, during the ' Challenger's ' Antarctic cruise. 5. The tail and 

 the caudal sjiiue of the newly hatched Nauplius are pushed in like the 

 tubes of a telescope, and covered by a thin cuticle, wliich 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 

 arc 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 Cypnis stage, terminate in the sucker of the 

 antenna), and are known under the name of cement-glands. Mouth 

 and anus are present. One pair of movable spines on the tail. First 

 "■ArcMzoea stage." 8. Length of Nauplius in the fourth stage 

 G millims. Three or four movable spines on the tail, with the six of 

 the next stage shining through the chitinous coverings. The glands 

 of the car.ipax are in connection with nerves, and present a large net- 

 work. No nerve-terminations on the lateral horns nor on the feelers. 



