14 



NATURAL HISTORY OF ARTHROPODS. 



of delicate mouth-parts, and over the outside of the stomach occur numbers of simple 

 glands, which are supposed to represent the liver. The nervous system (Fig. 17, C) is 

 upon the regular arthropodal type and needs no special description. Its principal 

 features can be made out from the figure, and its general relations are the same as in 

 other Crustacea. One thing, however, is of interest. For a long time the barnacles 

 were supposed to be without organs of vision, but in 1848 the eminent anatomist, Dr. 

 Joseph Leidy of Philadelphia, found the eyes in the Acorn Barnacle, JZalanus, and since 

 that time they have been found in many other species. In the form now under 

 discussion there is but a single eye present, and this is found as a small, dark spot in 



front of the mouth, and 

 completely covered by the 

 integument of the body. 

 Although to a superficial 

 glance this eye seems 

 single, it is in reality com- 

 posed of two, as is seen 

 from the fact that it re- 

 ceives a nerve on either 

 side (Fig. 17, C e). Of 

 course an eye of this simple 

 character and so enclosed 

 bv the skin cannot be of 



m 



use in distinguishing ob- 

 jects, but since the tissues 

 of the body are very trans- 

 lucent, this eye can recog- 

 nize the differences be- 

 tween light and shade. 



^j 



Of this ability, a ready 

 proof is attainable ; go to 

 some tidal pool where the 

 little white acorn barnacles 



FIG. 17. Anatomy of Lepas fascicularis. A. General anatomy: a. anus; 



c. cirri ; d. dorsal sinus ; e. adductor muscle ; f. filamentary ap- abound, and there watch 



pendages ; h. hepatic openings ; i. intestine ; 1. liver ; m. mouth ; 



o. ovary ; p. penis ; s. stomach ; t. testis : v. vas deferens ; v.c. the delicate and feathery 



carina ; v.s. scutum ; r.t. tergum. It. Mouth-parts. C. Nervous 



anatomy : a. antennal nerve ; c. nerves to cirri ; e. eye ; o. optic movements OI the C11T1, and 



ganglia; ce. CEsophageal commissure; s. supra-oesophageal ganglion. 



then suddenly pass the 



hand between them and the source of light, and instantly every foot will be withdrawn, 

 only to be put out again after some considerable time has elapsed. 



The barnacles are peculiar, in that they have no heart, and even distinct blood- 

 vessels are wanting. The blood Hows around between the different organs and 

 muscles, and is kept in motion by the movement of the various parts of the body. 

 There exists a large cavity in the dorsal region, which may be supposed to represent 

 the heart, but no distinct Avails are found and no traces of valves exist. In their 

 respiration the barnacles are equally degraded, the whole surface of the body aiding in 

 the aeration of the blood. 



The reproductive organs of the barnacles are, in comparison to the rest of the body, 

 very large. In each individual are to be found both male and female parts. The 

 former form finely lobular masses on either side or the body, communicating by fine 



