416 Dr. E. !S. Morse on the Early Stages 



son and Prof. Verrill. The specimens were found attached to 

 stones brought up in the dredge, and also adhering to the 

 lower valve of adult individuals, generally near the peduncle. 

 An examination of adidt individuals showed that while the 

 ovaries in some specimens were empty, in others they were 

 fully charged ; in some the ovaries would be partially empty, 

 in others the ovaries of one side would be nearly empty while 

 those of the other side would be quite full, bpecimens col- 

 lected by Prof. Verrill in August were found with eggs ; and 

 eggs were also noticed in specimens less than three six- 

 teenths of an inch in length. The eggs (PL XV. fig. 1) 

 were generally kidney-shaped, though very irregular as to 

 form and size ; they were spermaceti-white in colour, and 

 opaque, though having a central area translucent and appa- 

 rently depressed. In general outline they suggest the kidney- 

 shaped eggs of Fredericella. No intermediate stage was 

 observed between the ovarian q.^^ and the stage represented 

 in fig. 2. Tliis form recalled the general proportions of Ar- 

 cjiope and Mecjerlia, in being transversely oval, in having the 

 hinge-margin wide and straight, and in the presence of a 

 proportionally wide foramen. This stage was exceedingly 

 minute ; and only two individuals were discovered ; they were 

 attached to the rock, resting on the broad hinge-area. No- 

 thing could be traced of the structure, except an appearance of 

 granular contents, as indicated in the figure ; the shell showed 

 nothing of the scale-like structure so characteristic in later 

 stages. Between this stage and the next (fig. 3) the shell 

 rapidly elongates, while the hinge-margin remains nearly the 

 same in width ; this is also shown in the concentric lines of 

 growth seen faintly on the surface, indicating a rapid increase 

 in the length of the shell, while no corresponding increase 

 takes place in the widening of the hinge-margin. The pe- 

 duncle is longer than the shell, having distinct walls appa- 

 rently enclosing a clear interspace, the end slightly dilating 

 and forming a pear-shaped adhering disk. The structure of 

 the shell, of which more will be said in subsequent pages, 

 showed clearly the scale-like structure, with the caseal tubules 

 of the pallial lobes })crforating it. The anterior margin of the 

 pallial lobes gave rise to seven setas of variable lengths, all of 

 them projecting forward. These setaj, in nearly all instances, 

 were clothed with Dcsmids, and were probably available in 

 attracting sustenance to the animal ; they resembled in struc- 

 ture the sctai of the adult, as figured by Hancock; and the 

 longest of them was as long as the shell. The future position 

 of the calcareous loop was indicated by a strongly arched 

 process midway the length of the shell, from which sprang 



