Cuming 8 — Development of some Paleozoic Bryozoa. 49 



Art. Y. — Development of some Paleozoic Bryozoa • 

 by Edgar Roscoe C timings. 



Introduction. • 



The development of Paleozoic Bryozoa lias up to the present 

 time received very little attention. The few scattering obser- 

 vations of Lindstrom, 18 Nicholson,' 24 Shrubsole, 41 Vine," and 

 Dlrich,* 4 leave the knowledge of the subject practically where 

 it was at the outset. Nicholson devotes a chapter to a discus- 

 sion of the development of the Monticuliporidse, but does not 

 go further than a criticism of the views of Lindstrom, in regard 

 to the supposed ontogenetic relationship between Montiadipora 

 and Ceramopora. Shrubsole's notions of the development of 

 Fenestella are entirely erroneous, those of Yine are but little 

 better, while Ulrich concurs with Nicholson in rejecting the 

 views of Lindstrom. 



The writer's researches during the past year, at the Yale 

 University Museum, have resulted in the discovery of many 

 unique facts bearing upon the development of certain Paleozoic 

 and recent Bryozoa. Although this investigation is still in 

 progress, it will not be .out of place to present some of the 

 results thus far obtained, reserving the details for monographic 

 treatment later. 



All the material used in this investigation of the development 

 of Fenestella, Polypora, Unitrypa, Hemitrypa, Paleschara, 

 etc., belongs to the collection of the Yale University Museum. 

 The silicified Lower Helderberg and Hamilton Bryozoa were 

 especially collected by Dr. C. E. Beecher with reference to the 

 study of the stages of growth. Dr. Beecher has not only placed 

 all this unique material at the writer's disposal, but has in every 

 possible way lent his aid and encouragement to the work. For 

 this aid, as well as for his profound interest in the difficult and 

 too often neglected problems of paleobiology, the writer is 

 deeply grateful. 



General. 



The development of recent Bryozoa has been studied by a large 

 number of observers, among whom J. Barrois, 1-4 Calvet, 6a Clapa- 

 rede, 8 Harmer, 9 " 12 Joliet, 15 - 16 Metschnikoff, 21 "" Ostroumoff," 

 Pergens, 2 * Prouho, 29 " 31 KepiachofT, 32 - 38 Seeliger, 40 Smitt, 43 and 

 Yigelius 46 have contributed the most important results for the 

 presedentary stages; and Barrois, 1 Nitsche, 25 ' 26 Braem, 6 Daven- 

 port, 7 - 8 and Harmer, 11 ' 12a for the early budding stages of the col- 

 ony. While the latter are necessarily the only ones ever preserved 

 as fossils, a brief review of the earlier development will help to 

 make the discussion of the later much more intelligible. 



Am. Jour. Sci. — Fourth Series, Vol. XVII, No. 97.— January, 1904. 

 4 



