122 The Philippine Journal of Science wis 



pachychirus. These tubes are often 25 to 30 centimeters long 

 and 2 centimeters or more in diameter, but they may be much 



smaller than this. One end is 

 usually wider than the other 

 (fig. 2), and is firmly attached 

 to the rock while the rest of the 

 tube is fastened only at intervals. 

 Several branches with openings 

 may be present, the number 

 varying in different tubes. A 

 Fig. 2. Alga-tube of Aipheus pachychirus microscoplc examination shows 

 ■ ingTa°nche?"inroptn1nts.'^°'"' ^hat the tubes are nothing more 



than a dense mat of filamentous 

 algae so well worked together as to resemble a piece of loosely 

 woven cloth.* 



Whether the alga-tube is used by the aipheus as a shelter 

 throughout its life or whether it is only used during the breed- 

 ing season, I am unable to decide. Coutiere (1899) found Ai- 

 pheus pachychirus at Djibouti without the alga-tube, but he 

 attributed this to the scarcity of algse. Professor L. E. Griffin 

 in February, 1912, found about half-a-dozen tubes at Port 

 Galera, and in each case there were two individuals, supposedly 

 male and female, but neither was carrying eggs. During March, 

 April, and May, 1912, I collected 10 or 12 tubes from the same 

 locality and found with one exception a male and female in every 

 tube. In this exceptional case there was only a female present, 

 and she was ovigerous. 



In order to see the method of tube-making, the following sim- 

 ple experiments were undertaken. An alga-tube containing a 

 male and female aipheus was removed from a rock and slit open 

 from end to end, after which it was laid out as flat as possible 

 in the bottom of a dish of sea water. The two Crustacea were 

 then placed on the piece of matted alga where they remained 

 for some time, inactive, so far as construction was concerned. 

 Finally the male took advantage of a slight furrow in which 

 it was lying lengthwise, turned itself on its back, and using the 

 slender pair of chelate legs immediately back of the chelipeds 

 reached up and drew the sides of the furrow close together. 

 Then in the following manner it began to sew together the two 



* In the opinion of Dr. Marshall A. Howe, of the New York Botanical 

 Garden, this alga belongs to the Cyanophyceae and is a species of Plec- 

 tonenia closely allied to, and perhaps identical with, P. wollei Farlow. 

 The latter is a fresh-water form, however, while the former is marine. 



