ZOOLOGY AND BOTANY, MrCROSCOPY, ETC. 47 



Egg-envelope in Centropages hamatus. — Werner Busch (ZooL 

 Anmg., 19*20, 51, 201-5, 5 figs.). In this Copepod the typical ovum 

 {Ovum Impidum) shows a number of spine-like hollow processes of the 

 envelope, very variable in number and shape. The fresh-laid ovum is 

 spherical, and shows a delicate and transient plasmic membrane. Within 

 this the cytoplasm of the egg forms by retraction and secretion the 

 definitive envelope with its processes. The sea-water is the liberating 

 stimulus. J. A. T. 



New Species of Clavella on Cod. — W. Harold L kigh-Sharpe 

 {Joani. Marine Biol. Aasoc, 1920, 12, ;');)2-8, 9 figs.). The author bases 

 a new species, ClavelJa iadda, on specimens of a parasitic Copepod 

 collected by Michael (!. L. Perkins from cods. Compared with C 

 scialherica, the body is less globose, longer than wide ; the ovisacs are 

 tapering; there is a posterior trilobate genital process (as in G.irina 

 Wilson, but less pronounced) ; the cephalothorax is comparatively short, 

 little curved, and in line with the second maxillge ; the bulla is widest 

 at the apex of the sphere, not at the l)ase as in G. HciatJierica ; and 

 there is a slight difference in the mandibles. The ducts and apertures 

 of the renal excretory organs can be made out with great clearness on 

 the base of the second maxilla?. A provisional key to the species of 

 Clavella is submitted. J. A.. T. 



Cambrian Trilobites. — R. Etheridcie, Jun. {Trans. Proc. R. Soc. 

 S. Ai/slralia, J919, 43, 373-93, 2 pis). Au attempt to put in order 

 the remains of Cambrian Trilobites. There is seldom more than a 

 portion of a cephalon or pygidium preserved. In addition to the minute 

 Agnostus ellcedraensis there is perhaps only one weli-])reserved form, 

 that known as Ftychoparia alroiensis. J. A. T. 



Aunulata. 



Early Development of Scoloplos armiger. — H. C. Delsman 

 {Tijdschr. Nederland. Dierk. Ver., 191(i, 14, 383-498, 6 pis., 5 figs.). 

 In this Polycha3t the segmentation is very typical. Four quartettes are 

 formed. The first gives rise to the apical spot and the trochoblasts. 

 The second gives rise anteriorly to the secondary trochoblasts, a small 

 portion of the trunk ectoderm, and the stomodfeum ; and posteriorly to 

 almost the whole of the trunk ectoderm. The third gives rise anteriorly 

 to the stomodteum and ectomesoderm, and posteriorly to the ventral 

 ectoderm (neurotroch) and more ectomesoderm. The fourth quartette 

 gives rise anteriorly to the endoderm and posteriorly to the entomesoderm. 

 The other macromeres form the endoderm. Although the egg is one 

 of the largest Polychtet eggs as yet studied, there is not very al)undant 

 yolk. The endomeres are relatively small. The process of gastrulation 

 is neither epibole nor embole, but it is nearer the latter. There is a 

 somewhat irregular inward-gliding of endomeres, which arrange them- 

 selves to line the lumen. The early primordium of the larval pharynx 

 is like that of the radula-sac in Molluscs. The anus is late of appear- 

 ance and has no relation to the blastopore. There is a suppression of 

 the free-swimming trochophore stage ; what hatches out is a miniature 

 worm. J. A. T. 



