002 SUMMARY OF CURRENT RESEARCHES RELATING TO 



from which the prestercoral tuhc leads towards the yolk ; tho Mal- 

 pighian tubes arise from its dorsal wall, and tho author considers 

 that their position marks the prestercoral tuho as entodermic. Pass- 

 ing backwards from tho stomach is the postgastric tube, which is 

 so plugged with cells that its truo relations arc obscured ; it is probably 

 the most anterior region of tho mesenteron, the middle region of 

 which is still occupied by yolk. 



The eyes arc eight in number ; the anterior median pair have a 

 slightly different development from that of the remaining eyes. 

 A thickening of the ectoderm appears, and at ono end of this is an 

 invagination, directed obliquely to the surface, so that the outer wall 

 becomes inverted, whilst the cells of the lower wall retain their 

 original direction ; this consists of one layer, the inverted wall of 

 several layers. 



The epidermis meets above the invagination and gives rise to 

 the vitreous body ; the cuticle becomes thickened to form the lens ; 

 the cells of the inverted layer elongate and form the bacilli peri- 

 pherally, whilst the nuclei get pushed deeper down, so as to bo post- 

 bacillar ; the lower wall of the optic cup appears to give four pigment- 

 cells. 



In the other eyes, the nuclei of the retina are prebacillar. 



The lung-sacs arise as a pair of invaginations, and the lamella) are 

 first indicated by the nuclei of the cells being arranged in parallel 

 rows ; the cells give rise to a chitinous cuticle which coats the 

 lamella). 



At the end of the paper some results and theories of previous 

 authors are discussed in the light of the new facts observed by the 

 present author, and a bibliography closes the memoir. 



e. Crustacea. 



Structure and Development of Branchipus and Artemia.* — 

 What Prof. C. Claus did long ago for the Schizopoda in his monograph 

 on Nebalia, he has now even more completely achieved for the 

 Phyllopods in a detailed investigation of the structure and develop- 

 ment of Branchipus, nor is his research without rich results in 

 regard to the Malacostraca in general. 



I. The formation of metameres and the development of the body 

 during metamorphosis. — The newly liberated Branchipus larva, 

 though predominantly nauplioid, already exhibits hints of the mcta- 

 nauplius stage, in the presence, below the cuticle, of the maxillary 

 segments, of pad-like appendages on the next two joints, and of meta- 

 meric segmenting of the mesoderm band in the posterior portion. On 

 cross-section the cerebral and mandibular ganglia are seen still 

 connected with the ectoderm, the oesophageal ring and antennary 

 ganglia have already sunk inwards, while antennary gland, liver 

 diverticula, mouth, and hind-gut are readily apparent. The splanchnic 



*' Arbeit. Zool. lust. Univ. Wicn, vi. (1886) pp. 267-370 (12 pis.). 



