EXPLANATION OF PLATES. 

 As far as possible all figures made with the aid of a camera lucida. 



PLATE 18. 



Fig. 1. Crista franciscana sp. now Habit sketch, x 1. 



Fig. 2. C. franciscana. A portion of a colony showing method of 

 branching, and formation of ordinary and of ocecial internodes. The 

 ordinary uniserial internode consisting of a zooeeium (zoe.) giving origin 

 In I wo other zocecia (&''•)• The ooeeial internode consisting of the 

 zooeeium (ci.) the first member of the internode, the ocecium (oc), the 



second member, the z sium I '■. i. a third member. Arising from a basis 



rami(6a. r.) on the third zoeeeium is a fourth zooeeium (£*.), which serves 

 to continue the branch upward. The prominent ooecium (or.) having a well 

 devi loped tube (oest. I.) :tt its summit, bent slightly backward and upward. 

 X 3fi. 



Fig. 3. C. franciscana. A cross-section of an ovicell containing a 

 developing embryo in a young stage (emu.) and showing, also, an early 

 stage in the growth of the septum (sep.). 



Fig. -I. C. franciscana. Cross-section of an ovicell in an older stage 

 of growth, showing a relatively large embryo (emu.) and a septum (sep.) 

 whose growth is about completed. The chitinous tube (chi. t.) growing 

 down into the ocecial cone (oe. c.) shows only at intervals in this section. 



Fig. 5. C. edwardsiana. Diagrammatic representation of a cross-section 

 of the ovicell of C. edwardsiana showing the cellular septum (sep.) with 

 the chitinous tube (chi. t.) and chitinous floor (chi. //.). 



Fig. 6. Crisia geniculata. Milne-Edwards. Habit sketch, natural size. 

 X 1. 



Fig. 7. C. geniculata. A portion of a colony showing method of 

 branching, etc This, with position of ovicell and abbreviations, are iu 

 .•ill essentia] respeets what have just been given for ('. franciscana, iig. 2. 

 X 36. 



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