210 SUMMARY OF CURRENT RESEARCHES RELATING TO 



■y. Prototracheata. 



Development of Peripatus Novse-Zealandise.* — Miss L. Sheldon 

 has a further account "j" of her observations on the development of Peripatus 

 Novse-Zealandiae. The central nuclei of the segments of the yolk which 

 lie just beneath the periphery multiply much more rapidly than those 

 over the rest of the ovum. They thus come to form a special area, 

 which finally extends along about the middle third of the ovum, and 

 consists of a loosely reticulate mass of protoplasm which contains a large 

 number of nuclei. This area is triangular in form, and becomes more 

 compact, and flattens itself out to form the blastoderm. It grows round 

 the ovum till it covers about one-half of its surface, and the epibolic 

 growth continues until the blastoderm covers all but a very small space 

 in the middle of the ventral face of the ovum. Behind the uncovered 

 area, and in the middle line, there is a proliferation of nuclei, which, 

 in transverse section, gives rise to a keel-shaped mass of nuclei which 

 extends along the posterior half of the ovum ; round this space the 

 protoplasm becomes inflected, or forms a blastopore. This last increases 

 in length considerably, and becomes more open. The primitive streak 

 also becomes wider and deeper, and the primitive groove appears along 

 its centre. A small cavity, apparently homologous with the polar area 

 of P. capensis, appears and then disappears. Up to this stage there are 

 no signs of any cell-outlines, but the protoplasm forms a syncytium in 

 which nuclei are irregularly scattered. Want of material causes a large 

 gap in the observations at this point. After the appendages are formed, 

 the history of development is very similar to that of P. capensis, but it 

 is interesting to note that the duct of the first somite opens to the 

 exterior. 



The study of this new set of specimens has made the difference 

 between the developmental history of this species and that of P. capensis 

 less marked than it had previously been supposed to be. In fact, it is 

 rather strange that the almost total loss of yolk by the Cape species 

 should have apparently been accompanied by so few modifications in its 

 development. The material in hand does not allow of any statement 

 as to the mode or time of origin of the ectodermal yolk in P. Novse- 

 Zealandise, but as it appears in both species after the gastrula stage, it is 

 probably an ancestral feature in the development. 



The ova probably pass from the ovary into the uterus in December, 

 and the young are born in July ; to this, however, there are some 

 exceptions, as some January specimens contained embryos ready for 

 birth, and the embryos in one female vary somewhat in age. 



S. Araclinicla. 



Coxal Glands of Araclmida.| — Dr. J. C. C. Loman has examined the 

 coxal glands of six Arachnids, among which are Scorpio, Epeira, and 

 Phalangium ; on the whole he corroborates the results of those who have 

 preceded him in these investigations ; the organ in Phalangium is 

 described at somewhat greater length than those of the other types. He 

 cannot think there is any doubt about our having here the homologue 

 of a segmental organ, but he is not so certain that the coxal gland is the 



* Quart. Journ. Micr. Sci., xxix. (1888) pp. 283-93 (2 pis.). 



t See this Journal, 1888, p. 33. 



i Bijdragcn tot de Dieikuiide, xiv, (1887) pp. 89-96 (4 figs.). 



