C timings — Development of some Paleozoic Bryozoa. 55 



with the terms protegulum, protoconch, protaspis, etc., as 

 applied to the Brachiopoda, Cephalopoda, and Trilobita, 

 respectively; for the latter terms signify the initial shell or 

 covering of the individual and are not concerned with the 

 adult, while the protoecium is the initial zooecium of the col- 

 ony and belongs to all growth stages of the initial polypide later 

 than the kathembryo. From the standpoint of the colony the 

 stage represented by the protoecium is phylastic (figs. 27-30), 



31 



~=-c 



33 



Figures 31-35. — Types of free-swimming larvae. (Figures 31, 32, 34, 35, 

 after Barrois; figure 33, from Korschelt and Herder, after Barrois.) 



31. Larva of Alcyoniclium, a type which develops an alimentary canal; 

 32. Larva of Loxosoma; 33. Larva of Serialaria, vesicularian type ; 34. Larva 

 of Bugula, intestineless Chilostomatous type ; 35. Larva of the Cyphonaules 

 (Membranipora). 



r, retractile disc ; p and m, mantle cavity ; c, coronal cells ; o and py, pyri- 

 f orm organ ; s, adhesive organ (sucker) ; gl, glandular organ ; st, stomach ; 

 R, rectum ; ce, oesophagus. 



Figure 31 x 100 ; figure 32 x 116 ; figure 33 x 120 ; figure 34 x 133 ; figure 

 35 x66. 



The early development of the Cyclostomata presents some 

 peculiarities that led Barrois * to mistake the metembryo (fig. 16) 

 for a morula, and the early stages of the invagination of the 

 adhesive organ (figs. 17-19) for a gastrula. This mistake has been 

 repeated in a recent memoir on fossil Bryozoa. The develop- 

 ment of the Cyclostomata, as pointed out later by Barrois, 4 

 Ostroumoff, 27 and others, quite closely parallels the develop- 

 ment of the Chilostomata. The metamorphosis is similar. 



