Fig. 2. 



%\ 



LcA/c\r\r 



88 Mr. E. Ray Lankester's Zoological Observations 



The heart as known and described is an oval pellucid body, 

 with a dense mass at each pole. During 

 life it beats with marvellous rapidity, quite 

 unlike the action of a heart, and suggesting 

 (what I believe it is) a form of protoplasmic 

 movement allied to the ciliary. The mass 

 at each pole of the oval heart is seen in spe- 

 cimens about two thirds grown, when dilute 

 acid is added, to be a nucleated cell. From 

 each of these extends, not a contractile 

 membrane (as would appear from the figures 

 of Gegenbam-, Foil, and others), but from 

 twelve to twenty line processes or filaments 

 joining one cell to the other, leaving open 

 spaces between them. The rapid contractions 

 of these processes of the cells, which are not 

 unlike (except in being fixed at both ends) those pro- 

 cesses known as cilia, agitate the blood in which the heart 

 is suspended ; but there is no trace of blood-vessels connected 

 with the heart. In specimens of Appendicularia fiircata of 

 full size the heart was seen to be a little more complex in 

 structin-e ; for at the base of each fibre or process of the 

 two original large conical cells (which still retain their form 

 and their large nuclei) is developed a small swelling with a nu- 

 cleus (fig. 2). Moreover each of the fibres is now seen (when 

 treated with picric acid) to possess a transverse striation, like 

 that of the muscular fibres of the great tail or flabellum. I 

 have specimens of Appendicularia furcata, treated with picric 

 acid and mounted in glycerine, which exliibit admirably at 

 the present moment this very remarkable structure of the 

 heart. 



Histology of Sipunculus nudus. 



Every naturalist who visits Naples studies this very in- 

 teresting and abundant Avorm more or less, and comes to a 

 conclusion respecting its generative organs differing from those 

 of his predecessors. [ can only briefly state on the present 

 occasion the results of my study of this worm, as to the his- 

 tology of which I have a mass of drawings and preparations. 



First, as to the coi-puscles of the perivisceral fluid. These 

 are the pink corpuscles, the amoeboid, the mulberry corpuscles 

 of various sizes (usually regarded as testicular cell-masses), the 

 ova, and the detached portions of the peritoneal membrane, and 

 the ''Topfchen" or ciliated globes. These last were especially 

 studied recently by Brandt ; he did not ascertain their origin ; 

 he is mistaken in his statements as to "cilise capitatfe." The 



