Grube, the rudiment of the sheath of the still unformed 

 proboscis. The wall of the intestinal canal, or yolk sac, 

 consists at this time of large cells. Later, by means of a 

 circular twist of the most anterior part of the body, the 

 caudal disc develops and the proboscis is formed, which the 

 larva can let out and pull in. The digestive canal is formed 

 in this way. On the intestinal canal extensions appear, and 

 in addition to this, it is divided into three parts. The 

 anterior and posterior parts are significantly thinner than 

 the middle one which composes the future stomach. In the last 

 the more enlarged lateral pouches appear. Later on the eyes 

 develop; at first they have the form of circular red spots. 

 The vascular system develops, and, on the dorsal side of the 

 body, the pulsating heart first becomes noticeable. 



Grube finished the description of his observations with 

 the following words: "The development considered here is 

 probably spread extensively in the class ANNULATA. This 

 is established on the basis of detailed investigations on many 

 representatives of Naidae and Lumbricinae namely in Saenuris 

 variegata Hoffm., Euaxes acutirostris Gr. and Lwnbvioulus 

 variegatus Gr., and if it can be judged by an analogy with 

 the adult animals, it will be also correct for the genus 

 Lumbricus, and also for many sea worms" Cp. 45). With this, 

 Grube carefully observed that discussion of analogy without 

 special investigations can lead to erroneous conclusions. 



A discussion of Grube' s work leads to the conclusion 

 that he promoted the study of embryology of the annulated 

 worms (annelids) and discovered phenomena the detailed study 

 of which was done significantly later. His most important 

 achievement in terms of recent embryology can be summarized 

 in the following way: 



1. Grube established that in the eggs of Proboscidea 

 leeches there are polar plasmas; especially conspicuous are 

 protoplasmic rings on the animal pole. 



2. He recognized the complete, unequal division of the 

 ovum of Proboscidea leeches, during which the animal polar 

 plasma can go in one of the blastomeres of the four-celled 

 stage. 



526 



