74 



Presents. 



[Nov. 28, 



fertile brown body. The latter can be easily detected in stained 

 colonies at this stage, and its remains may be seen even in colonies 

 which have been mounted dry. Its position differs from that of the 

 ordinary brown bodies, which are situated at a deeper level in the 

 colony. 



The communication between the fertile zooecium and the young 

 ovicell permits of the passage of the embryonic structures into the 

 cavity of the latter. The fertile brown body, which remains a con- 

 spicuous object for a long period, is usually found in the ovicell, not 

 far from the zooecium in which it was produced ; and it forms a kind 

 of centre from which the lobes of the branching embryophore pass 

 out. The primary embryo has meanwhile divided repeatedly, so 

 that the ovicell contains a large number of secondary embryos, some 

 of which are already developing into larva?, and others are still 

 undergoing division. 



A definite relation thus exists between the size of the colony and 

 the extent to which the ovicell or the embryo has developed, although 

 variation in these respects occurs within rather wide limits. This 

 fact is illustrated by series of measurements. 



The healthy development of the embryos is shown to depend on the 

 functional activity of the polypides, which no doubt nourish the 

 developing larva3. There are reasons for believing that complete 

 degeneration of the polypides does not ordinarily take place at a time 

 when their activity is required for the nourishment of the ovicell. 



Some details are given with regard to the changes which take 

 place in the older colonies, and particularly with regard to the 

 secondary thickening of the calcareous matter and to the develop- 

 ment of new broods of embryos. 



It would hardly be possible to find two Cyclostom.es which are 

 more different from one another than are Crista and Lichenopora, 

 The fact of the occurrence of embryonic fission in both genera, 

 accompanied as it is by complete dissimilarity of details, may be taken 

 as affording strong grounds for believing that the existence of 

 embryonic fission is a fundamental phenomenon which occurs 

 throughout the Cyclostomata. 



Presents, November 28, 1895. 



Transactions. 



Berlin :— Gesellschaft fur Erdkunde. Zeitschrift. Bd. XXX, 

 No. 5. 8vo. Berlin 1895. The Society. 



Dorpat : — Imperial University. Uchenuiya Zapiski. 1894. Nos. 

 2 — 4. 1895. Nos. 1 — 2. 8vo. Jurjew ; [Dissertations. 

 1894-95.] [Russian.'] 8vo. Jurjetv, &c. The University. 



