530 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Fertilisation of Cyclops.* * * § — Herr J. Riickert describes tlie phenomena 
of fertilisation in Cyclops strenuus Fisch. There are three opinions in 
the field as regards the origin of the centrosomes and spheres of the first 
cleavage spindle : — (1) That both centrosomes come from the spermato- 
zoon, but some who accept this derive the spheres from the ovum ; (2) that 
the centrosomes have a paternal and maternal origin, and Fol’s quadrille 
is corroborated by several ; (3) that in different cases they differ in 
their origin, they may be maternal or paternal, or both. 
In Cyclops , the second directive spindle has a tangential position, 
and the second polar nucleus remains in the ovum ; it is drawn inwards, 
and is subsequently seen inside one of the blastomeres. Neither polar 
bodies nor germinal vesicle show centrosomes, attraction-spheres, or 
rays. The sperm-nucleus has an irregular sphere, but no visible centro- 
some. The first sphere buds off a second. The spheres of the first 
cleavage nucleus are derived solely from those of the sperm-nucleus, and 
the position of the latter, to which the female pronucleus adapts itself, 
determines the direction of the first cleavage. 
Revivification of Dried Copepods and Copepod Ova.f — Prof. C. 
Claus reviews the literature on this subject, and, having experimented 
with mud 10 years old, shows that species of Diaptomus , like Phyllopods 
and Ostracods, survive desiccation in the ovum stage, while species of 
Cyclops survive only in the Cyclopid stages and as adult sexual forms. 
In Diaptomus there is a hard ovarian sac which forms a protective 
capsule, while that of Cyclopidae is delicate. The same paper contains 
a discussion of Milcrocyclops diaphanus Fisch, which is equivalent to 
M. minutus Claus. 
Freshwater Ostracoda.$ — Prof. C. Claus describes the internal 
structure of Cypris and other Ostracods. He first discusses the ali- 
mentary canal and excretory organs. Inter alia he notices that in the 
secretory activity of the mid-gut, it seems normal that the stumps of 
the cells which have liberated the secretion-products should themselves 
regenerate. The shell-gland, which seems to correspond to the an- 
tennary gland of other forms, is minutely described, as also the maxillary 
gland. The nervous system shows a pyriform brain, a broad sub- 
oesopliageal ganglion (mandibular and maxillary), and a nerve-chain 
whose halves are in part distinctly separate. As many as six pairs of 
ganglia are recognisable. The complex musculature is briefly described. 
There seem to be no blood-corpuscles, a fact which may be associated 
with the minuteness of the body. In Cytheridae and Cypridse the dorsal 
vessel and heart are also absent, and respiratory appendages are only 
known in the Cypridinid genera Asterope and Monopia. 
Systematic Position of Trilobites.§ — Mr. H. M. Bernard calls atten- 
tion to the recent papers by Dr. C. E. Beecher on the appendages and 
structure of Triarthrus. The metastoma, now revealed for the first 
time, exhibits the first stages of the modification which leads to the 
arrangement which obtains in Apus. The position of the labium in 
* Anat. Anzeig., x. (1895) pp. 708-25 (8 figs.), 
t Arbeit. Zool. Inst. Univ. Wien, xi. (1895) pp. 1-12 (2 pis.), 
t Tom. cit., pp. 17-18 (5 pis.). 
§ Quart. Journ. Geol. Soc., li. (1895) pp. 352-9 (1 fig.). 
