PA RASITIC COPEFODS—CALIGID.E— WTLSON. 515 



])()iHtiiio- diagonally outward. And tinally in ('(iVkju^ fm^ (iml Lepe- 

 opliiliih'ux <l!s><iiin(latus the}^ appear to be made up of two pai'ts, differ- 

 ing- considerahlj in size, the smaller part being anterior in the ('(ilujns 

 and posterior in the Lepeoj)]ithrii'ax species. A section of one of these 

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

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

 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 capal)le 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 

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

 muscles, and l)etween the bands of connective tissue in the body wall. 

 The propelling agent of these l)lood 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 \)\'\o\ to 

 reversal, the motion consists of a simple oscillation l)ack and forth, 

 without any deffnite movement in either direction. 



The course of the ])lood streams v^aries so much in the difl'erent spe- 

 cies that it would l)e necessary- to describe each separately. T"'he only 

 descriptions given are for CaUgus curfus ])y Pickering and Dana (1838), 

 and for LepeojjJdJii'J nix jxcfordl !s 1)v A. Scott (l^^Ol), 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 

 alimentar}" canal. A pair of lateral currents start from the region 

 just behind the e^^es, and each flows outward and backward to the tip 

 of the lateral lobe on its side. It then turns forward along the lateral 

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

 mandibles where it turns toward the median line. 



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

 course ])ackward 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 they turn 



