I'M! A STTIC COPEPODFl—CALIGIDJE— WILSON. 515 



pointing- diagonally outward. And finally in Caligvs teres and Lepe- 

 ophtfa irus dissimulatus they appear to be made up of two parts, differ- 

 ing considerably in size, the smaller part being anterior in the Caligus 

 and posterior in the Lepeophtheirus species. A section of one of these 

 glands shows it to lie divided into small lobules much like a pancreas, 

 and in the center of each lobule can be seen the divisions of the duct 

 for collecting the secretion. 



THE BLOOD AND CIRCULATION. 



The blood is made up of a colorless fluid in which floats numerous 

 corpuscles also colorless. These corpuscles are of different sizes and 

 shapes and are even capable of being changed in shape to accommodate 

 the diameter of the spaces through which they pass. There is no 

 heart nor blood vessels of any sort. The circulation is entirely lacu- 

 nar, and consists of an irregular pulsation or streaming of the blood 

 back and forth through the spaces left around the internal organs and 

 muscles, and between the bands of connective tissue in the body wall. 

 The propelling agent of these blood streams seems to be the peristaltic 

 movements of the alimentary canal and the respiratory movements of 

 the rectum. And since the peristaltic movements pass from the 

 anterior to the posterior for a portion of the time and then are 

 reversed, so in like manner the blood streams continue to flow in one 

 direction for a short time and then slacken and reverse. And, again, 

 since the movements of neither the intestine nor the rectum are uni- 

 form or continuous, so those of the blood current are spasmodic and 

 irregular. Often also, particularly at the times of slackening prior to 

 reversal, the motion consists of a simple oscillation back and forth, 

 without any definite movement in either direction. 



The course of the blood streams varies so much in the different spe- 

 cies that it would be necessary to describe each separately. The only 

 descriptions given are for Caligus curt us by Pickering and Dana (1838), 

 and for Lepeophtheirus pectoralis by A. Scott (1901), and these vary in 

 many essential particulars. 



The following general statements will apply to all the species so far 

 observed. There is a central current along the median line under the 

 alimentary canal. A pair of lateral currents start from the region 

 just behind the eyes, and each flows outward and backward to the tip 

 of the lateral lobeon its side. It then turns forward along the lateral 

 margin of the carapace till it reaches the muscles connected with the 

 mandibles where it turns toward the median line. 



A second pair of lateral currents start from nearl}' the same region, 

 course backward through the thoracic area and the free segment into 

 the genital segment. Here they turn outward, following the repro- 

 ductive organs to the posterior end of the segment, where the} 7 turn 



