Development of the Pectinihranchiata, 439 



asserts that from these eggs an embryo is developed, which 

 swallows as many as it can of the " egg-like bodies," and that, 

 being thus furnished with materials, it proceeds in its develop- 

 ment. When the embryo cannot catch the crushed " egg-like 

 bodies," it dies from want of nourishment. 



It is easy to see that Dr. Carpenter has fallen into an error, 

 and it is to be regretted that he should have allowed himself to 

 be misled by a prejudice, as owing to this his observations have 

 become obscure and confused. It is incomprehensible how he 

 could imagine that he could distinguish the true eggs from 

 the " egg-like bodies " only by the difference which he professes 

 to find in their segmentation, as he ought also to know that the 

 segmentation is sometimes very different even in animals of the 

 same species ; and he states that the segmentation in Purpura 

 lapillus is very irregular. The segmentation, however, is his 

 sole point of support, for he himself says that, with the excep- 

 tion of this, the eggs enclosed in the capsules (even his " egg- 

 like bodies," as well as his true eggs) are anatooiically and 

 physiologically alike. In one word, he could find no perceptible 

 difference. 



In this we agree with Dr. Carpenter. In our memoirs we 

 have proved that all the bodies which are enclosed in the cap- 

 sules have a chorion and a vitelline membrane, and that their 

 segmentation is not arrested by the commencement of the act of 

 conglomeration. We have shown that all these eggs may be 

 included in this act, but that in each capsule there are usually 

 one or several eggs which become developed before the act of 

 conglomeration has commenced, and that the embryos which 

 are developed by these isolated eggs die very soon from the de- 

 ficiency of material necessary for the formation of the organs. 

 It is these embryos developed from a single egg which have led 

 Dr. Carpenter astray : he has seen a plank of safety for his ideas 

 of unity, and it is for this reason that he has made his creatures 

 devour everything which might alter the law which he believes 

 to be the foundation of all development. Thus, as soon as the 

 embryos previously mentioned were formed, they would pro- 

 ceed to unite themselves with the conglomerated eggs to seek 

 their nourishment : for this reason they would be furnished with 

 a mouth and an oesophagus. Dr. Carpenter has given us the 

 figure of such a mouth and oesophagus, both beset with cilia ; 

 and then, by the agency of this mouth they would attach them- 

 selves to the conglomerate. Here, however, is his greatest error ; 

 for what he gives us as the mouth and oesophagus is the foot in 

 its different stages of development. 



This occurs in the following way. The foot, in its first de- 

 velopuient, projects and slightly passes the rest of the common 



